Chemical Dictionary

AAbiotic EnvironmentThe part of an ecosystem that includes the nonliving surroundings.

Abrasive A hard and wear-resistant material that is used to wear, grind or cut away other material.

Absolute HumidityThe ratio of the mass of water vapour to the volume occupied by a mixture of water vapour and dry air.

Absolute PressureGage pressure plus atmospheric pressure.

ORAbsolute Pressure is the sum of the available atmospheric pressure and the gage pressure in the pumping system

Absolute Pressure (PSIa) = Gauge Pressure + Atmospheric Pressure

Absolute Pressure TransducerA transducer which measures pressure in relation to zero pressure (a vacuum on one side of the diaphragm).

Absolute ViscositySee Viscosity

Absolute ZeroTemperature at which thermal energy is at a minimum. Defined as 0 Kelvin, calculated to be -273.15°C or -459.67°F.

AbsorbanceAbsorbance (A) is defined as -log(1-α) = log(1/τ), where α is the absorptance and τ the transmittance of a medium through which a light beam passes.

Absorbed DoseFor any ionising radiation, absorbed dose (D) is the mean energy imparted to an element of irradiated matter divided by the mass of that element.

AbsorbentsAbsorbents are material that take up or absorb any liquids or vapours that come in contact with it.

ORA material that extracts one or more substances from a fluid (gas or liquid) medium on contact, and which changes physically and/or chemically in the process. The less volatile of the two working fluids in an absorption cooling device.

AbsorptionIn chemistry absorption can mean two things: Firstly it can imply that powerful forces exist holding two substances together, and that seperation of the two is not easily accomplished. Secondly it can mean absorption of heat, light etc.. . The absorption of ultraviolet, visible and

infrared radiation is the basis of some forms of spectrometry which can be used to identify different chemical compounds. See also infrared radiation.

ORAbsorption is an operation in which a gas mixture is contacted with liquid for preferentially dissolving one or more constituents of gas and providing a solution of them in liquid.

Absorption CoefficientAbsorption coefficient (a) is the relative decrease in the intensity of a collimated beam of electromagnetic radiation, as a result of absorption by a medium, during traversal of an infinitesimal layer of the medium, divided by the length traversed.

Absorption Coefficient, MolarMolar absorption coefficient (ε) is absorption coefficient divided by amount-of-substance concentration of the absorbing material in the sample solution (ε=a/c). The SI unit is m2mol-1. Also called extinction coefficient, but usually in units of dm3cm-1mol-1.

AbsorptivityAbsorptivity is the fraction of incident radiations absorbed. It may be denoted by letter ‘a’.

AbundanceSee Natural Abundance

Acceleration Measure of how fast velocity is changing, so we can think of it as the change in velocity over time. The most common use of acceleration is acceleration due to gravity which can also appear as the gravitational constant (9.8 m/s2).

ORA change in the velocity of a body or particle with respect to time. The parameter that an accelerometer measures (dv/dt). Units expressed in "g".

AccelerometerA device which converts the effects of mechanical motion into an electrical signal that is proportional to the acceleration value of the motion. A sensor. A transducer.

AccuracyComparison to an accepted standard.

ORThe closeness of an indication or reading of a measurement device to the actual value of the quantity being measured. Usually expressed as ± percent of full scale output or reading.

AcetylAny chemical compound with an acetate group.

AcidAcid is a type of compound that contains hydrogen and dissociates in water to produce positive hydrogen ions. The reaction, for an acid HA is commonly written:

HA ⇌ H+ + A-

In fact, the hydrogen ion (the proton) is solvated, and the complete reaction is:HA + H2O ⇌ H3O+ + A-

This definition of acids comes from the Arrhenius theory. Such acids tend to be corrosive substances with a sharp taste, which turn litmus red and give colour changes with other indicators. They are referred to as protonic acids and are classified into strong acids, which are almost completely dissociated in water (e.g. sulphuric acid and hydrochloric acid), and weak acids, which are only partially dissociated (e.g. acetic acid and hydrogen sulphide).

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The strength of an acid depends on the extent to to which it dissociates, and is measured by its dissociation constant.In the Lowry-Brønsted theory of acids and bases (1923), the definition was extended to one in which an acid is a proton donor (a Brønsted acid), and a base is a proton acceptor (a Brønsted base). An important feature of the Lowry-Brønsted concept is that when an acid gives up a proton, a conjugate base is formed that is capable of accepting a proton.

acid⇌ base + H+

Similarly, every base produces its conjugate acid as a result of accepting a proton.base + H+ ⇌ acid

For example, acetate ion is the conjugate base of acetic acid, and ammonium ion is the conjugate acid of ammonia.

As the acid of a conjugate acid/base pair becomes weaker, its conjugate base becomes stronger and vice versa.

A further extension of the idea of acids and bases was made in the Lewis theory. In this, a G. N. Lewis acid is a compound or atom that can accept a pair of electrons and a Lewis base is one that can donate an electron pair. This definition encompasses "traditional" acid-base reactions, but it also includes reactions that do not involve ions, e.g.

H3N: BCl3 H3NBCl3

in which NH3 is the base (donor) and BCl3 the acid (acceptor).OR

It is a water soluble sour tasting chemical compound. An acid has pH less than 7. The molecule contains hydrogen and are sour tasting compounds and their generic formula is AH.

ORCompound that gives off H+ ions in solution.

ORA substance that when dissolved in water dissociates and can donate a hydrogen (proton) to another molecule. Examples include sulphuric acid and nitric acid. Under these conditions nitric acid dissociates according to the following equation:

HNO3 ⇌ H+ + NO3-

Nitric Acid Proton Nitrate ion

In water the protons attach themselves to the water molecules, giving the following equation:

HNO3 + H2O ⇌ H3O+ + NO3-

Nitric Acid Water Hydroxonium ion Nitrate ion

Acid Dissociation ConstantAcid dissociation constant (Ka) is the equilibrium constant for the dissociation of an acid HA through the reaction

HA + H2O ⇌ A- + H3O+

The quantity pKa = -log Ka is often used to express the acid dissociation constant.pKa = -log Ka

Acid RainA term used to describe precipitation that has become acidic (low pH) due to the emission of sulfur oxides from fossil fuel burning power plants.

Acidic Describes a solution with a high concentration of H+ ions. Acoustics

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The degree of sound. The nature, cause, and phenomena of the vibrations of elastic bodies; which vibrations create compressional waves or wave fronts which are transmitted through various media, such as air, water, wood, steel, etc.

Actinides The actinides (actinons or actinoids) are the fourteen elements from thorium to lawrencium inclusive, which follow actinium in the periodic table. The position of actinium is somewhat equivocal and, although not itself an actinide, it is often included with them for comparative purpose. The series includes the following elements: thorium (Th), protactinium (Pa), uranium (U), neptunium (Np), plutonium (Pu), amercium (Am), curium (Cm), berkelium (Bk), californium (Cf), einsteinium (Es), fermium (Fm), mendelevium (Md), nobelium (No) and lawrencium (Lr). Every known isotope of the actinide elements is radioactive. Traces of Pa, Np and Pu are consequently found, but only Th and U occur naturally to any useful extent.

ORThis is a group of elements within the periodic table and are also known as the transuranics. The name refers to those elements with increasing atomic no. from actinium, which all have similar chemical properties, like the lanthanides. The first few members of the group are the naturally occuring elements actinium, thorium, proactinium and uranium. Beyond this elements have been made artificially by radioactive bombardment. These artificial elements are unstable, some have very short lifeimes and undergo spontaneous radioactive decay.

Activated SludgeAn active population of microorganisms used to treat wastewater, or the process in which the organisms are employed.

Activation EnergyIn general, activation energy is the energy that must be added to a system in order for a process to occur, even though the process may already be thermodynamically possible. In chemical kinetics, the activation energy is the height of the potential barrier separating the products and reactants. It determines the temperature dependence of the reaction rate.

ORIt is the minimum energy required to start a chemical reaction.

ActivityActivity (a) is a thermodynamic function used in place of concentration in equilibrium constants for reactions involving nonideal gases and solutions. For the species i activity is defined as

a = f × cwhere ai is the activity of the species i, ci is its molar concentration, and fi is a dimensionless quantity called the activity coefficient.

ORA thermodynamic term for the apparent or active concentration of a free ion in solution. It is related to concentration by the activity coefficient.

Activity CoefficientActivity coefficient (γ or f) is a fractional number which when multiplied by the molar concentration of a substance in solution yields the chemical activity. This term gives an idea of how much interaction exists between molecules at higher concentration.

ORA ratio of the activity of species i(ai) to its molality (C). It is a correction factor which makes the thermodynamic calculations correct. This factor is dependent on ionic strength, temperature, and other parameters.

Individual ionic activity coefficients, f+ for cation and f- for an anion, cannot be derived thermodynamically. They can be calculated only by using the Debye-Huckel law for low concentration solutions in which the interionic forces depend primarily on charge, radius,

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and distribution of the ions and on the dielectric constant of the medium rather than on the chemical properties of the ions.

Mean ionic activity coefficient (f±) or the activity of a salt, on the other hand, can be measured by a variety of techniques such as freezing point depression and vapour pressure as well as paired sensing electrodes. It is the geometric mean of the individual ionic activity coefficients: f± = (f+n+f-n-)1/n

AdditivesIn the manufacturing process of plastics, polymer is just one constituent. Their are other chemicals like impact modifiers, colorants, reinforcements, plasticisers and stabilizers etc that give specific properties to the plastics. These are called additives.

Adhesive A substance that bonds together the surfaces of two other materials.

ORAny compound that can stick two surfaces together is classified as an adhesive. Simple adhesives are of cellulose, starch and rubbers. Modern adhesives are based upon complex polymeric materials. The adhesive is spread in an unpolymerised form, and the adhesive properties increase as polymerisation occurs between the two surfaces.

Adiabatic Expansion/CompressionExpansion (or compression) of a gas (e.g. air) without exchange of heat with the surroundings. Air cools upon expansion and heats up upon compression, and this is the main reason for the vertical temperature gradient seen in the lower atmosphere (i.e. the troposphere). The adiabatic temperature gradient in dry air is near 1°C for every 100 m change in elevation. The actual gradient on Earth is less because of the presence of water in the air.

Adiabatic ProcessAdiabatic process is a thermodynamic process in which no heat enters or leaves the system. In general, an adiabatic change involves a fall or rise in temperature of the system.

ORA chemical or mechanical process which takes place without heat entering or leaving the system. The term is only applicable to enclosed and isolated systems - so in essence is idealistic and purely theoretical and is important in the study of thermodynamics.

ORWithout loss or gain of heat to a system. An adiabatic change is a change in volume and pressure of a parcel of gas without an exchange of heat between the parcel and its surroundings.

AdrenalineThis was the first naturally produced hormone to be isolated it a pure state. It is known as epinephrine, but its chemical name is 1-[3,4-dihydroxyphenol]-2-methylaminoethanol. Its main action is to raise blood pressure, producing a faster pulse rate.

AdsorptionAdsorption is a process in which molecules of gas, of dissolved substances in liquids, or of liquids adhere in an extremely thin layer to surfaces of solid bodies with which they are in contact.

ORA surface phenomena in which a solute (soluble material) concentrates or collects at a surface (the adsorbent).

OR

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If any compound, solid, liquid or gas, is loosely held by weak attraction to the surface of a solid it is said to have undergone adsorption. This process is much weaker and less permanent than absorption.

ORIt is the attachment of a molecule of gas or liquid to the surface of another substance (usually solid). These molecules form a closely adherent film or layer held in place by electrostatic forces, that are considerably weaker then chemical bonds. Adsorption takes place only at the surface, which includes all capillaries, cracks, depressions, openings and other type of irregularities.

Advanced Wastewater TreatmentThe removal of any dissolved or suspended contaminants beyond secondary treatment, often this is the removal of the nutrients nitrogen and/or phosphorus.

AerationIntimate contact of the atmosphere and water to add air (oxygen) to the water. The term is also applied to gas stripping where an undesirable gas is removed from the water.

AerobesOrganisms which require molecular oxygen as an electron acceptor for energy production.

Aerobic ProcessA process which requires molecular oxygen.

AerosolAerosols are colloidal dispersions of liquid or solid particles in a gas, as in a mist or smoke. The commonly used aerosol sprays contain an inert propellant liquefied under pressure. The pressure of the gas causes the mixture to be released as a fine spray (aerosol) or foam (aerogel) when a valve is opened.

ORAny small particle, solid or fluid, that is suspended in air. Abundance values typically range from 100 to 10,000 particles per cubic centimeter for air over land with higher values found in cities. Sizes vary greatly, but typically are near 0.1 μm or less. The particles originate from wind-blown sea-salt or dust, volcanic eruptions, burning of vegetation, combustion of coal and petroleum products, and other natural and anthropogenic processes. Aerosol particles serve as nuclei for condensation of water droplets and for growth of ice crystals and also influence the radiation balance directly. In the lower stratosphere, concentrations are extremely low; much of the aerosol here consists of droplets of sulfuric acid.

AgrochemicalChemicals, like hormone, fungicide, or insecticide, that improve or protects the crop production.

AirThe air that we breathe is a mixture of gases. The composition of dry-air at sea level is shown:

Gas Percentage Gas Percentage

NitrogenOxygenArgonCarbon Dioxide

78.00820.950.930.03

NeonHeliumKryptonXenon

0.0180.00050.00010.00005

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Air Set CementA cement that sets through loss of water.

AlbedoMeaning "whiteness,? albedo is a measure of the reflectivity of a surface. If a surface has an albedo of 40%, it means that 40% of the light falling on a surface is reflected. The planetary albedo of Earth is its reflectivity as seen from space (near 30%). Also, there is cloud albedo and ground albedo. The ocean, on the whole, has a low albedo, as do forests. The deserts have high albedo, while fresh snow has the highest albedo of the common surfaces on Earth.

AlchemySeveral of the great Greek philosophers considered all matter to be composed of four basic "elements", fire, air, earth and water, and that all materials were had these components mixed in different proportions. If this theory was true, then it was believed that all substances could be converted (transmuted) into each other by varying the proportions of the mixture. This tansmutation theory was the basis of Alchemy from approx. 300 B.C. to 1500 A.D., after which it slowly gave way to the more scientific concepts of chemistry from the 17th century onwards. The alchemists represented their "element" by a variety of symbols (see figure), some of which were based on astrological signs

They were mainly concerned with trying to turn base metals into gold and looking for the elixir of life although they also developed medicinal drugs, developed couterfeiting techniques and the debasement of precious metals.

AlcoholsAlcohols are compounds in which a hydroxy group, -OH, is attached to a saturated carbon atom.

ORAlcohol in chemistry means any organic compound in which a hydroxyl group (OH) is bound to a carbon atom, further bound to other hydrogen and/or carbon atoms.

ORAn organic compound with one or more hydroxyl "-OH" groups.

ORAn organic compound which has the general formula CnH2n+1OH, they consist of hydrocarbon chains terminated by hydroxyl groups, O-H. Smaller members are water soluble, flammable and are useful as organic solvents and fuels. As with hydrocarbons, each member differs from the previous by an additional -CH2- group. Alcohols with branced chains are also possible.

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AldehydesAldehydes are broad class of organic compounds having the generic formula RCHO, and characterized by unsaturated carbonyl group (C=O). They are formed from alcohols by either dehydrogenation or oxidation. Their chemical derivation is indicated by the name al(cohol) + dehyd(rogenation).

ORAn important starting material and intermediate in organic synthesis. Many aldehydes of industrial significance are used as solvents, perfumes, and flavouring agents or as intermediates in the manufacture of plastics, dyes, and pharmaceuticals.

ORAn organic compound with a carbonyl group (C=O) at one end of a hydrocarbon group.

ORAn organic compound containing the -CHO group. An example of these distinct aromatic compounds is formaldehyde.

Alicyclic CompoundsAn alicyclic compound contains rings of -CH2- units joined by single bonds. Their general formula is CnH2n, the simplest member being cyclopropane. An example of these compounds is cyclohexane (see below):

Aliphatic CompoundsAliphatic compounds are acyclic or cyclic, saturated or unsaturated carbon compounds, excluding aromatic compounds.

ORAny organic compound in which the main structure is a chain of carbon atoms joined to each other.

AlkaliA compound that has the ability to neutralize an acid to form a salt. A substance which is somewhat irritating or corrosive to the skin, eyes and mucous membranes. Turns red litmus paper to blue. Common strong alkalis are sodium and potassium hydroxide.

ORA water soluble hydroxide on one of the alkali metals. The term is virually synonymous with the term base. An example is Sodium Hydroxide (NaOH).

Alkali MetalsAlkali metal is a term that refers to six elements: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). These elements make up group 1 of the periodic table of elements. They all form singly charged positive ions, and are extremely reactive. They react violently with water, forming hydroxides and releasing hydrogen gas and heat. Caesium and francium are the most reactive and lithium is the least.

ORGroup I of the periodic table consists of the alkali metals. They are the most electropositive elements known, are monovalent, have low melting points and react violently with water.

Alkaline Earth MetalsAlkali earth metal is a term that refers to six elements: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These elements make up group 2 of the periodic table of elements. They all exhibit a single oxidation state, +2. They are all light and very reactive. Barium and radium are the most reactive and beryllium is the least.

Chemists to denote slightly soluble metal oxides formerly used the term "earth". The oxides of barium, strontium, and calcium resemble alumina (Al2O3), a typical "earth", but form alkaline mixtures with water. For this reason barium, strontium, and calcium were called

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alkaline earth metals. This name has now been extended to include all of the elements of group 2.

ORGroup II of the periodic table consists of the alkaline earth metals. They are bivalent and react with water to produce water soluble hydroxides.

AlkalinityThe capacity of a water to neutralize acids.

AlkaloidsAlkaloids are basic nitrogen organic compounds (mostly heterocyclic) derived from plants and having diverse pharmacological properties. Alkaloids include morphine, cocaine, atropine, quinine, and caffeine, most of which are used in medicine as analgesics or anaesthetics. Some alkaloids are poisonous, e.g. strychnine and coniine, and colchicine inhibit cell division.

ORA naturally occuring organic compound containing nitrogen that acts as a base. Many alkaloids are physiologically active and can be used in small quantities as medicines, but if taken in larger doses they can be extremely poisonous. An example is caffeine.

AlkanesAlkanes (paraffins) are acyclic branched or unbranched hydrocarbons having the general formula CnH2n+2, and therefore consisting entirely of hydrogen atoms and saturated carbon atoms. In systematic chemical nomenclature alkane names end in the suffix -ane. They form a homologous series (the alkane series) methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), etc. The lower members of the series are gases; the high-molecular mass alkanes are waxy solid. Generaly the alkanes are fairly unreactive. They form haloalkanes with halogens when irradiated with ultraviolet radiation. Alkanes are present in natural gas and petroleum.

ORThis is the correct chemical term for compounds known as paraffins. They are considered the simplest organic compounds and are a family of chain hydrocarbons having the general formula C2H2n+2. All of the bonds are single bonds (-C-H-, and -C-C-). The chains can be straight or branched. The smaller members (less than 4 carbons) are gases, while larger ones (five to seventeen carbons) are liquids. Beyond seventeen carbons the alkanes are waxy solids.

AlkenesAlkenes are acyclic branched or unbranched hydrocarbons having one or more double carbon-carbon bonds in their molecules. In systematic chemical nomenclature, alkene names end in the suffix -ene. The general formula is CnH(2n+2)-2x were x is the number of double bonds. Alkenes that have only one double bond form a homologous series: ethene

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(ethylene), CH2=CH2, propene, CH3CH2=CH2, etc. Alkenes typically undergo addition reactions to the double bond.

ORThese compounds are similar to alkanes, in that they can be straight or branched aliphatic hydrocarbons. The only difference is that the alkenes (also known as olefins) contain a carbon-carbon double bond, and have the general formula C2H2n. The simplest group member is ethene which is a gas. The double bond can be anywhere within the length of the carbon chain, resulting in a large number of possible isomers. The double bond means that these compounds are "unsaturated" and react readily with compounds capable of adding across the double bond. Some simple alkenes are listed below:

ORUnsaturated hydrocarbons that contain one or more carbon-carbon double bonds.

Simple Alkenes

EthenePropene

H2C=CH2

H2C=CHCH3

1-Butene2-Butene

H2C=CHCH2CH3

H3CHC=CHCH3

AlkylationAlkylation is a reaction in which an alkyl group is added to a compound. In petroleum refining, it normally means reaction of an olefin with an iso-paraffin to produce a larger iso-paraffin having higher octane number. There are two modes of alkylation :

1) Thermal Alkylation2) Catalytic Alkylation

AlkynesAlkynes (acetylenes) are acyclic branched or unbranched hydrocarbons having a one or more triple carbon-carbon bond. In systematic chemical nomenclature alkine names end in the suffix -yne. The general formula is CnH(2n+2)-4x where x is the number of triple bonds. Alkynes that have only one triple bond form a homologous series: ethyne (acetylene), CH≡CH, propyne, CH3CH≡CH, etc. Like alkenes, alkynes undergo addition reaction.

ORThese compounds are also similar to alkanes. They have the general formula C2H2n-2 corresponding to carbon chains with a triple carbon-carbon bond included. The simplest member of this family is ethyne (also known as acetylene). The triple bond makes these compounds very reactive. Some simple alkynes are listed here:

AllChemEAlliance for Chemical Sciences and Technologies in Europe. The representative body for chemistry and chemical engineering in Europe.

AllotropyAllotropy is the occurrence of an element in two or more crystalline forms.

ORCertain chemical elements have the ability to exist in two or more different structural forms known as allotropes. These allotropes may possess different physical properties such as density and melting points. Allotropic elements include carbon, tin, phosphorus and sulphur. Each allotrope is stable within a certain range of temperature and pressure only, and under certain conditions an allotrope can be converted into another.

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Alloy A metallic solid or liquid formed from an intimate combination of two or more elements.

ORAn alloy consists of an intimate mixture of two elements, usually metals to give a metal compound or solid solution. Bronze is an alloy of copper and tin and brass on of copper and zinc. By varying the composition it is possible to alter the chemical and physical properties of the alloy such as conductivity, ductility and corrosion resistance.

Alpha ParticleAlpha particle is a helium nucleus emitted spontaneously from radioactive elements both natural and manufactured. Its energy is in range 4-8 MeV and is dissipated in a very short path, i.e. a few centimetres of air or less than 0.005 mm of aluminium. As a helium nucleus consists of two protons and two neutrons bound together as a stable entity the loss of an alpha particle involves a decrease in nucleon number of 4 and decrease of 2 in the atomic number. A stream of alpha particles is known as an alpha ray or alpha-radiation.

ORThese are helium nuclei (no electrons) produced in nuclear reactions. They are helium ions, He+2.

ORThese are particles possessing a positive charge, and are emited from radioactive elements. The particles are actually helium nuclei, ie. helium atoms that had lost their outer electrons. The study of the alpha particle played a major part in the development of modern atomic theory. Rutherford bombarded other elements with alpha particles to produce nuclear disintegration.

AlphanumericA character set that contains both letters and digits.

Alternating Copolymer A polymer, composed of two different repeating mers, in which the different mer units systematically alternate positions along the molecular chain.

AlumAn alum is a double salt comprising a sulphate salt of a monovalent element, with the sulphate salt of a trivalent element. The most well known example is potash alum (aluminium potassium sulphate) KAl(SO4)2.12H2O which is used to clear murky water.

AlumelAn aluminum nickel alloy used in the negative leg of a Type K thermocouple (Trade name of Hoskins Manufacturing Company).

AmalgamLiquid mercury has the ability to dissolve other metals to produce alloys and these alloys are called amalgams. Amalgam examples are gold/mercury, silver/mercury and copper/mercury all of which are used in dentistry.

Ambient CompensationThe design of an instrument such that changes in ambient temperature do not affect the readings of the instrument.

Ambient ConditionsThe conditions around the transducer (pressure, temperature, etc.).

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Ambient PressureThe average or mean pressure of the surrounding air which comes in contact with the equipment and instruments under test.

Ambient TemperatureThe average or mean temperature of the surrounding air which comes in contact with the equipment and instruments under test.

ORThe temperature of a medium, such as gas or liquid, which comes into contact with or surrounds an apparatus or building element.

AmideAn organic compound containing the -CONH2- group (see below). Also see peptide.

Amines

Amines are compounds formally derived from ammonia by replacing one, two, or three hydrogen atoms by hydrocarbyl groups, and having the general structures RNH2 (primary amines), R2NH (secondary amines), R3N (tertiary amines).

ORAmines are organic compounds containing nitrogen. Here one or more hydrogen atoms are replaced by alkyl groups or other groups where the nitrogen is bonded to a carbon atom in the group. Amine are used in rubber, dyes, pharmaceuticals, and synthetic resins and fibres and in a host of other applications.

ORAn amine is a distinctive smelling organic compound with one or more of the hydrogen atoms in ammonia replaced by organic groups. There are three classes of amines, dependant on the number of hydrogens replaced (see below):

The organic groups can be aliphatic, alicyclic or aromatic, and some common amines are listed below:

Amino AcidsAmino acids are compounds containing both a carboxylic acid group (-COOH) and an amino group (-NH2 ). The most important are the a-amino acids, in which the -NH2 group in attached to the C atom adjacent to the -COOH group. In the β-amino acids, there is an intervening carbon atom.

ORA functional group which consists of a carbon with a carboxylic acid, "-COOH" and an amine, "-NH2." These compounds are the building blocks for proteins.

OR

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A large class of substances with molecules including the amino and carboxyl groups.In the human body, amino acids are joined together to form long chains as part of the structures of proteins. Because they possess two functional groups, amino acids exhibit both acidic and basic characteristics. Each amino acid has an abbreviation when in a protein chain, so that the protein GlyAlaVal would indicate that a molecule of Glycine is joined to one of Alanine which is in turn joined to one of Valine.

Amino GroupAn organic compound containing the -NH2- group. Substances which contain this group are called amines. Examples include urea, and trimethylamine.

Amorphography The branch of science concerned with the determination of amorphous solid structures and their systemmatic classification (see also crystallography).

Amorphous SolidA noncrystalline solid with no well-defined ordered structure.

ORSolid having no long-range order.

AmpereAmpere (A) is the SI base unit of electric current.The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2×10 -7 newton per metre of length.

ORThe ampere is the basic unit of electric current. It is that current which produces a specified force between two parallel wires which are 1 metre apart in a vacuum. It is named after the French physicist Andre Ampere (1775-1836).

ORA unit used to define the rate of flow of electricity (current) in a circuit; units are one coulomb (6.28 x 1018 electronics) per second.

AnabolismBiosynthesis, the production of new cellular materials from other organic or inorganic chemicals.

AnaerobesA group of organisms that do not require molecular oxygen. These organisms, as well as all known life forms, require oxygen. These organisms obtain their oxygen from inorganic ions such as nitrate or sulfate or from protein.

Anaerobic ProcessA process which only occurs in the absence of molecular oxygen.

AngstromÅngström (Å) is a unit of length equal to 10-10 m. The Ångström is defined in terms of the wavelength of the emission spectra's red line of an atom of cadmium (6438.4696 Å).

AnhydrideAny chemical compound obtained, either in practice or in principle, by the elimination of water from another compound.

OR

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These are compounds formed by the removal of water or Hydrogen and Oxygen together from another substance. In inorganic chemistry most anhydrides are formed by the loss of the water of crystallisation. eg. Copper(II) sulphate is a blue hydrated salt with the formula CuSO4.5H2O, but if heated, the water is driven off leaving the colourless anhydrous salt CuSO4. In organic chemistry an anhydride is usually the result of the loss of a water molecule from a dicarboxylic acid, eg. from phthalic acid to give phthalic anhydride.

AnionAnion is a negatively charged atomic or molecular particle.

ORA negatively charged ion or group of atoms.

Anion ExchangeAn anionic resin has negative ions built into its structure and therefore exchanges positive ions. In anion exchange, the side groups are ionized basic groups, such as (-NH2, -NRH, -NR2, -NR3

+) to which anions OH- are attached. The exchange reaction is one in which different anions in the solution displace the OH- from the solid.

AnisotropyAnisotropy is the property of molecules and materials to exhibit variations in physical properties along different molecular axes of the substance.

ORExhibiting different values of a property in different crystallographic directions.

Annealing A generic term used to denote a heat treatment wherein the microstructrure and, consequently, the properties of a material are altered. Frequently, refers to heat treatment whereby a cold-worked metal is softened by allowing it to recrystallize.

Anode The electrode where electrons are lost (oxidized) in redox reactions.

Anoxic ProcessA process which occurs only at very low levels of molecular oxygen or in the absence of molecular oxygen.

AnthropogenicOf, made, or caused by human activity or actions.

Antiferromagnetism A phenomenon observed in some materials in which complete magnetic moment cancellation occurs as a result of antiparallel coupling of adjacent atoms or ions. The macroscopic solid possesses no net magnetic moment.

AntifreezeA substance added to a material or to a system to prevent freezing. Specially, water soluble substances, such as ethylene glycol, glycerol, or ethyl alcohol, are added to the water in the radiator of of an internal combustion engine to prevent freezing at low external temperatures.

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Antiknocking AgentA substance commonly added to the fuel of an internal combustion engine to prevent premature excessively rapid and irregular combustion of the fuel-air mixture. The knocking properties of various fuels vary widely with their chemical structures and are expressed by their octane rating. One of the widely used anti-knocking agents is Methyl tert-butyl ether (MTBE)

AntioxidantsA substance which decrease the rate at which another substance is oxidised. An example includes BHA.

AntiparticleAntiparticle is a particle having the same mass as a given elementary particle and a charge equal in magnitude but opposite in sign.

ArAr is symbol for element argon.

AresAre (a) is a unit of area equal to 100 m2. The unit is still used in agriculture.

Area Measures the size of a surface using length measurements in two dimensions.

ArenasArenes are monocyclic and polycyclic aromatic hydrocarbons. See aromatic compounds.

Aromatic CompoundsAromatic compounds are major group of unsaturated cyclic hydrocarbons containing one or more rings, typified by benzene, which has a 6-carbon ring containing three double bonds. All the bonds in benzene (C6H6) are the same length intermediate between double and single C-C bonds. The properties arise because the electrons in the p-orbitals are delocalised over the ring, giving extra stabilization energy of 150 kJ/mol over the energy of Kekulé structure. Aromatic compounds are unsaturated compounds, yet they do not easily partake in addition reactions. Historical use of the term implies a ring containing only carbon (e.g., benzene, naphthalene), but it is often generalized to include heterocyclic structures such as pyridine and thiophene.

ORAromatics, so called because of their distinctive perfumed smell, are a group of hydrocarbons including, mainly, benzene, toluene and the xylenes. These are basic chemicals used as starting materials for a wide range of consumer products. Almost all aromatics come from crude oil, although small quantities are made from coal.

ORA substance containing one or more benzene rings. These compounds although unsaturated do not undergo normal reactions for unsaturated compounds as shown by their saturated open-chain analogues. This ability is related to the way in which their bonding electrons are spread evenly over the planar ring. Substances classified as being aromatic include those with one benzene ring such as:

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or several rings such as:

Certain other compounds can posses aromatic character - ie. they react in an aromatic manner even though they do not have the six-membered carbon ring. This group of compounds includes:

AsphaltIt is a black, semisolid, sticky substance, composed of bitumen and mineral matter, derived from petroleum through the evaporation of some of the lighter hydrocarbons, and partial oxidation of the remainder. It consists of mainly complex hydrocarbons, made artificially by adding mineral matter to bitumen. It is used in road making, building and in paints and varnishes.

Associativity A property in math which states that: (A+B)+C=A+(B+C) and (A*B)*C=A*(B*C)

ASTMAmerican Society for Testing and Materials.

Astronomical UnitAstronomical unit (AU) is a unit of length employed in astronomy for describing planetary distance. It is the mean distance of the earth from the sun, equal to 1.49597870×1011 m.

Atactic A type of polymer chain configuration wherein side groups are randomly poitioned on one side of the polymer backbone or the other.

ORA polymer is atactic if the groups attatched to the backbone are not arranged in any regular geometric pattern. Also see Isotactic.

Atlantic Heat ConveyorThe considerable heat transfer from south to north by near-surface waters moving across the equator in the Atlantic. This movement is required to balance a southward flow of water in the ocean depths. This deep water, called the "North Atlantic Deep Water," moves sluggishly but the flow is considerable - some 20 Sverdrup - and is rather cold (between about 2°C and 4°C). So since the North

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Atlantic trades cold water for warm, it gains lots of heat in the process. This is the reason regions well north of 60°N, such as in Scandinavia, have comparably mild climates. The graph below shows the flow of heat (in units of 1013 Watts) across the present Atlantic (?+? symbol), across the Atlantic during glacial times (?o? symbol), and the world ocean average (thick solid line bordered by thin lines that represent the upper and lower limits ). The general trend to take from the graph is that heat is transported from southern to northern latitudes.

AtmospheresCommon units for measuring pressure.

Atmospheric DistillationMode of distillation, that is carried out at atmospheric pressure or pressure slightly above atmospheric pressure.

Atmospheric PressureThe pressure of the air at sea level; one standard atmosphere at zero degrees centigrade is equal to 14.695 pounds per square inch (1.033 kilograms per square centimeter).

AtomThis is the smallest particle of a chemical element.

ORAtom is the basic building block of chemistry. Atoms, also called chemical elements, can combine with one another to form compound. It is the smallest unit of matter that cannot be decomposed into simpler substances by ordinary chemical processes.

ORThe smallest object that retains properties of an element. Composed of electrons and a nucleus (containing protons and neutrons).

ORThe smallest part of an element that retains its properties. It is possible to "split" the atom up further into components; protons - which have a positive charge, electrons, which have a negative charge and neutrons which have no charge. The simplest atom is hydrogen, which consists of a single proton nucleus and has a single electron forming an orbit or shell around the proton. The next simplest is helium, with two protons and two neutrons in the nucleus with two electrons orbiting within the shell - see below for diagram:

In all atoms the number of protons and electrons are the same but the number of neutrons can vary. Most of the mass of an atom is composed of the protons and neutrons, while the different isotopes of the same element vary in their number of protons, neutrons and electrons in the atomic structure. In some elements the arrangement of protons and neutrons in the nucleus is unstable, and the atom may disintegrate forming radioactivity.

Atomic Mass (Atomic Weight)It is the average mass of the isotopes of an element. It is the decimal number on the periodic chart. It depends upon both the isotopes' masses and the amount of each isotope present.

OR

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The mass of a neutral atom of a nuclide. The atomic weight of an atom is the weight of the atom based on a scale where 12C = 12. The atomic weight of an element is the weighted average of each isotope.

ORSee Relative atomic mass

Atomic NumberAtomic number (Z) is a characteristic property of an element, equal to the number of protons in the nucleus.

ORIt is the number of protons in the nucleus of an atom. It is the whole number on the periodic chart. It is also the number of electrons in a neutral atom (where protons = electrons).

ORThe number of protons in the nucleus

Attached Growth ReactorA reactor in which the microorganisms are attached to engineered surfaces within the reactor. Examples of attached growth reactors are the trickling filter and the rotating biological contactor.

Austenite Face-centered cubic iron; also iron and steel alloys that have the FCC structure.

Auto CatalysisA condition obtained when one of the products of a reaction, or one of the factors, acts as a catalyst and changes the rate of reaction. Eg. In the hydrolysis of esters, the acid product formed exert an influence to increase the velocity of hydrolysis. Autocatalysis may be positive or negative, depending on whether the result of the catalytic action is acceleration or retardation.

Auto Catalytic ReactionSee Auto Catalysis

Autoignition TemperatureAutoignition temperature is the minimum temperature required to initiate or cause self-sustained combustion in any substance in the absence of a spark or flame. This varies with the test method.

AutotrophicOrganisms which utilize inorganic carbon for synthesis of protoplasm. Ecologists narrow the definition further by requiring that autotrophs obtain their energy from the sun. In microbiologist parlance, this would be a photoautotroph.

AutotrophsA group of organisms capable of obtaining carbon for synthesis from inorganic carbon sources such as carbon dioxide and its dissolved species (the carbonates). This group includes plants and algae.

Avogadro ConstantAvogadro constant (NA or L) is the number of elementary entities in one mole of a substance.

L = N / nIt has the value (6.022 045 ± 0.000 031) × 1023 mol-1.

Avagadro's Number

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Number representing the number of molecules in one (1) mole: 6.023 * 1023.

AzeotropeAzeotrope is a mixture of two liquids that boils at constant composition, i.e. the composition of the vapour is the same as that of the liquid. Azeotropes occur because of deviations in Raoult's law leading to a maximum or minimum in the boiling point - composition diagram. The composition of an azeotrope depends on the pressure.

ORA specific mixture of components, which at a given pressure cannot be separated by distillation, i.e. the liquid and vapour phases have the same compositions.

The dew pointand bubble point are identical at azeotropic composition and mixture vaporizes at single temperature.

Azeotropic DistillationThe process of distillation, wherein the third component is added to the binary azeotrope to effect the complete separation.

Azo CompoundsAzo compounds are organic compounds containing the group -N=N- linking two other groups. They can be formed by reaction of a diazonium ion with a benzene ring.

Azo DyeAn azo dye is one of an extensive range of synthetic organic dye made from aniline, by first converting it with sodium nitrite to a diazonium chloride salt which is then reacted with other aromatic amines, phenols and sulphonic acids. The well known indicator methyl-orange is formed by making the diazo salt of sulphanilic acid, and reacting the product with dimethylaniline (see below):

All azo compounds have the general formula Ar-N=N-Ar' with the characteristic -N=N- group in the middle.

B

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BacteriaOne celled microorganisms which do not have a nuclear membrane.

ORSingle-celled organisms, free-living or parasitic, that break down the wastes and bodies of dead organisms, making their components available for reuse by other organisms.

BaffleA device, such as a steel plate, used to check, retard, or divert a flow of a material.

Bainite A Fe-C composition consisting of a fine dispersion of cementite in alpha-ferrite. It is an austenitic transformation product that forms at temperatures between those at which pearlite and martensite transformations occur.

Ball MillsBall mills, also known as centrifugal or planetary mills, are devices used to rapidly grind materials to colloidal fineness (approximately 1 micron and below) by developing high grinding energy via centrifugal and/or planetary action.

Band Gap Energy For semiconductors and insulators, the energies that lie between the valence and conduction bands.

BarBar (bar) is a unit of pressure equal to 105 Pa. Its use is temporarily maintained with the SI. The milibar (100 Pa) is commonly used in meteorology.

BarrelBarrel (US, petrol) is an American unit of capacity usually employed in the petroleum industry and trading in fuels (barell = 158.9872949 L).

BaseSubstance which gives off hydroxide ions (OH-) in solution.

ORHistorically, base is a substance that yields an OH - ion when it dissociates in solution, resulting in a pH>7. In the Brønsted definition, a base is a substance capable of accepting a proton in any type of reaction. The more general definition, due to G.N. Lewis, classifies any chemical species capable of donating an electron pair as a base. Typically, bases are metal oxides, hydroxides, or compounds (such as ammonia) that give hydroxide ions in aqueous solution.

ORA substance that reacts with acid to produce a salt and water only. It does this by accepting a hydrogen ion from the acid. An example is ammonia which accepts a proton to become the ammonium ion - NH4

+

Basic Having the characteristics of a base.

BecquerelBecquerel (Bq) is the SI derived unit, with a special name, for radioactivity, equal to s -1. It describes a radioactivity of an amount of radionuclide decaying at the rate, on average, of one spontaneous nuclear transition per second. The unit is named after the French scientist A. H. Becquerel (1852-1908) (disintegrations per unit time), equal to s-1.

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Beer's lawBeer's law is the functional relationship between the quantity measured in an absorption method (A) and the quantity sought, the analyte concentration (c). As a consequence of interactions between the photons and absorbing particles, the power of the beam is attenuated from P0 to P. Beer's law can be written

A = log (P0/P) = abcwhere a is a proportionality constant called the absorptivity and b is the path length of the radiation through the absorbing medium. Also called the Beer-Lambert law.

Beta DecayNuclear decay by emission of an electron or a positron. Positron decay is always accompanied by electron capture decay.

Beta-Delayed Particle EmmissionWhen a large amount of decay energy is available, the nucleus may emit:

Neutrons Protons Alpha particles following the beta decay.

Beta Particles These are the electrons produced in nuclear reactions.

ORBeta particle is a charged particle emitted from a radioactive atomic nucleus either natural or manufactured. The energies of beta particles range from 0 to 4 MeV. They carry a single charge; if this is negative, the particle is identical with an electron; if positive, it is a positron.

An unstable atomic nucleus changes into a nucleus of the same mass number but different proton number with the emission of an electron and an antineutrino (or a positron and a neutrino)

ORRadioactive elements can emit several types of radiation. Beta particles are very fast moving electrons. The particles have a velocity of between 30-99% speed of light, and it is this velocity which gives the beta particles greater penetrating power than alpha particles.

Beta RadiationStreams of beta particles are known as beta ray or beta radiation. Beta rays may cause skin burns and are harmful within the body. A thin sheet of metal can afford protection to the skin.

Bifunctional Monomer A monomer unit that has two active bonding positions.

BiocideBiocides are formulations of one or more active substances which can kill or control viruses, bacteria, algae, moulds or yeasts.

Biochemical Oxygen Demand (BOD)The amount of oxygen required to oxidize any organic matter present in a water during a specified period of time, usually 5 days. It is an indirect measure of the amount of organic matter present in a water.

ORThe weight of oxygen taken up mainly as a result of the oxidation of the constituents of a sample of water by biological action; expressed as the number of parts per million of oxygen taken up by the sample from water originally saturated with air, usually over a period of five

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days at 20 degrees centigrade. A standard means of estimating the degree of contamination of water.

BiofilmA film of microorganisms attached to a surface, such as that on a trickling filter, rotating biological contactor, or rocks in natural streams.

BiogasBiogas is a mixture of methane and carbon dioxide resulting from the anaerobic decomposition of such waste materials as domestic, industrial, and agricultural sewage. Methanogenic bacteria carry out the decomposition; these obligate anaerobes produce methane, the main component of biogas, which can be collected and used as an energy source for domestic processes, such as heating, cooking, and lighting.

Bio MassAs defined by the Energy Security Act (PL 96-294) of 1980, "any organic matter which is available on a renewable basis, including agricultural crops and agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, and aquatic plants."

Biogeochemical cycleThe cycle of elements through the biotic and abiotic environment.

BiosynthesisCatabolism, the production of new cellular materials from other organic or inorganic chemicals.

BlackbodyIn radiation physics, an ideal blackbody is a theoretical object that absorbs all the radiant energy falling upon it and emits it in the form of thermal radiation. Planck's radiation law gives the power radiated by a unit area of blackbody, and the Stefan-Boltzman law expresses the total power radiated.

ORA theoretical object that radiates the maximum amount of energy at a given temperature, and absorbs all the energy incident upon it. A blackbody is not necessarily black. (The name blackbody was chosen because the color black is defined as the total absorption of light energy.)

Blackbody RadiationBlack body radiation is the radiation emitted by a perfect black body, i.e., a body which absorbs all radiation incident on it and reflects none. The wavelength dependence of the radiated energy density ρ (energy per unit volume per unit wavelength range) is given by the Planck formula

ρ = [8πhc / λ5 (ehc / λkT – 1)]where λ is the wavelength, h is Planck's constant, c is the speed of light, k is the Boltzmann constant, and T is the temperature.

Block Copolymer A linear copolymer in which identical mer units are clustered in blocks along the molecular chain.

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BODSee biochemical oxygen demand.

BODu

See Ultimate Biochemical Oxygen Demand

Body-centered Cubic (BCC) A common crystal structure that contains atoms located at the corners of a cubic cell and one atom at the cell center position.

Bohr MagnetonBohr magneton (μB) is the atomic unit of magnetic moment, defined asμB = eh/4πme = 9.274×10-24 A m2

where h is Planck's constant, me the electron mass, and e the elementary charge. It is the moment associated with a single electron spin.

Bohr's Atom Bohr made significant contributions to the atom. He understood the line spectra-- the reason why only certain wavelengths are emitted when atoms jump down levels.

Boiling PointBoiling point is the temperature at which the liquid and gas phases of a substance are in equilibrium at a specified pressure. The normal boiling point is the boiling point at normal atmospheric pressure (101.325 kPa). Boiling point of a liquid increase with increase in pressure and vice-versa.

Boltzmann's Constant The gas constant per molecule: 1.381x10-23J/atom K; 1.381x10-16 erg/atom K; or 8.63x10-5

eV/atom K.OR

Boltzmann constant (k) is the molar gas constant R divided by Avogadro's constant. It has the value 1.380658×10-23 J/K.

BondA chemical link between two atoms. In an ionic bond the attraction is between opposite charges on two neighboring ions. In a covalent bond the two atoms share a pair of electrons.

Bond - Covalent It is the sharing of electrons. There is no rip off because the ionization energies of the atoms are not drastically different in magnitude. The result is neither atom is strong enough to remove the electron from the other atom. (Like two kids of equal strength trying to take a ball away from each other. They both can only hold on to it, neither succeeding in taking it and thus they are bonded).

Bond - IonicIt is formed by electron transfer (the rip off). An element whose electrons are loosely held (first and second columns of chart) surrenders its outer electron(s) to an element with high ionization energy (that therefore has a high electron affinity). The latter are the right hand side of the chart (like the halogens). When the transfer is completed, we have ions produced. The unlike charges of the ions holds them together electrically. Hence, the ionic bond. Elements from opposite sides of the chart have very different ionization energies, so that one atom is strong enough to rip off electrons from the other.

Bonding Energy The energy required to separate two atoms that are chemically bonded to each other.

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Born-Haber CycleBorn-Haber cycle is a cycle of reactions used for calculating the lattice energies of ionic crystalline solids. For a compound MX, the lattice energy is the enthalpy of the reaction

M+(g) + X-(g) → M+X-(s) ΔHL

The standard enthalpy of formation of the ionic solid is the enthalpy of the reactionM(s) + 1/2X2(g) → M+X-(s) ΔHf

The cycle involves equating this enthalpy (which can be measured) to the sum of the enthalpies of a number of steps proceeding from the elements to the ionic solid. The steps are:

1) Atomization of the metalM(s) → M(g) ΔH1

2) Atomization of the nonmetal1/2X2(g) → X(g) ΔH2

3) Ionization of the metalM(g) → M+(g) + e- ΔH3

This is obtained from the ionization potential.4) Ionization of the nonmetal

X(g) + e- → X-(g) ΔH4

This is electron affinity.5) Formation of the ionic solids

M+(g) + X-(g) → M+X-(s) ΔHL

Equation the enthalpies givesΔHf = ΔH1 + ΔH2 + ΔH3 + ΔH4 + ΔHL

from which ΔHL can be found.

Boyle’s LawBoyle's law is the empirical law, exact only for an ideal gas, which states that the volume of a gas is inversely proportional to its pressure at constant temperature.

V = T/PBragg AngleBragg angle (θ) is defined by the equation

nλ = 2dsinθwhich relates the angle θ between a crystal plane and the diffracted x-ray beam, the wavelength λ of the x-rays, the crystal plane spacing d, and the diffraction order n (any integer).

Bragg's Law A relationship that stipulates the condition for diffraction by a set of crystallographic planes.

Branched Polymer A polymer having a molecular structure of secondary chains that extend from the primary chains.

Brass A copper-rich copper-zinc alloy.

Brazing A metal joining technique that uses a molten filler metal alloy having a melting temperature greater than about 425 ° C. BrineWater saturated or strongly impregnated with salt.

British Thermal Unit

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The quantity of thermal energy required to raise the temperature of one pound of water at its maximum density by 1 degree F. One BTU is equivalent to .293 watt hours, or 252 calories. One kilowatt hour is equivalent to 3412 BTU.

BremsstrahlungX-rays produced when fast electrons pass through matter. The bremsstrahlung (German for "slowing-down radiation") energy varies from 0 to the energy of the electron.

Brittle Fracture Fracture that occur by rapid crack propagation and without appreciable macroscopic deformation.

Bronze A copper-rich copper-tin alloy.

Brownian MotionBrownian motion is the continuous random movement of small particles suspended in a fluid, which arise from collisions with the fluid molecules. First observed by the British botanist R. Brown (1773-1858) when studying pollen particles. The effect is also visible in particles of smoke suspended in a still gas.

BTUSee British Thermal Unit

Bubble PointUpon heating a liquid mixture, this is the point at which bubbles first appear.

ORIt is the temperature at which the liquid mixture of given composition starts to vaporize as the temperature is increased.

BufferBuffer is a solution designed to maintain a constant pH when small amounts of a strong acid or base are added. Buffers usually consist of a fairly weak acid and its salt with a strong base. Suitable concentrations are chosen so that the pH of the solution remains close to the pKa of the weak acid.

ORAny substance or combination of substances which, when dissolved in water, produces a solution which resists a change in its hydrogen ion concentration on the addition of an acid or alkali.

Buffer CapacityA measure of the ability of the solution to resist pH change when a strong acid or base is added.

Buffer Solutions Solutions that resist changes in their pH, even when small amounts of acid or base are added.

Bulk DensityThe weight of a material per unit of volume compared to the weight of the same volume of water.

Burgers Vector A vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.

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Burning PointThe temperature at which a material ignites.

CCalcination

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A high-temperature reaction whereby one solid material dissociates to form a gas and another solid.

CalibrationThe process of adjusting an instrument or compiling a deviation chart so that its reading can be correlated to the actual value being measured.

Calomel ElectrodeCalomel electrode (calomel half cell) is a type of half cell in which the electrode is mercury coated with calomel (Hg2Cl2) and the electrolyte is a solution of potassium chloride and saturated calomel. In the calomel half cell the overall reaction is

Hg2Cl2(s) + 2e- ⇄ 2Hg(l) + 2Cl-

The standard electrode potential is  Electrode potential SHE, V

T, °C 0.1 M KCl 3.5 M KCl sat. KCl

15 0.3362 0.254 0.2511

20 0.3359 0.252 0.2479

25 0.3356 0.250 0.2444

30 0.3351 0.248 0.2411

35 0.3344 0.246 0.2376

CalorieThe quantity of thermal energy required to raise the temperature of one gram of water by 1°C at 15°C.

ORThe amount of heat required to raise the temperature of a unit of water, at or near the temperature of maximum density, one degree Celsius (or Centigrade [C]); expressed as a "small calorie" (the amount of heat required to raise the temperature of 1 gram of water by one degree C), or as a "large calorie" or "kilogram calorie" (the amount of heat required to raise one kilogram [1,000 grams] of water one degree C); capitalization of the word calorie indicates a kilogram-calorie.

Calorific ValueThe amount of heat liberated by the combustion of a unit quantity of a fuel under specific conditions.

ORThe amount of heat produced from the complete combustion of a unit quantity of fuel. Higher (or gross) calorific or heating value is that when all products of combustion are cooled to the pre-combustion temperature, water vapour formed during combustion is condensed, and necessary corrections have been made. Lower (or net) heating value is obtained by subtracting from the gross heating value the latent heat of vaporization of the water vapour formed by the combustion of the hydrogen in the fuel.

ORCalorific value of a fuel is the total quantity of heat librated, when a unit mass (or volume) of the fuel is burnt completely. Higher or Gross calorific value – Usually all fuels contain some hydrogen and when the calorific value of hydrogen containing fuel is determined experimentally, this hydrogen is converted into steam. If the products of combustion are condensed to the room temperature (15°C or 60°F) the latent heat of condensation of steam also gets included in the measured heat, which is then called higher or gross calorific value. So, it is equal to the total amount of heat produced, when a unit mass / volume of a fuel has been burnt completely and the products of combustion have been permitted to cooled to room temperature.

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Lower or Net calorific value – in actual use of any fuel, the water vapour and moisture etc. are not condensed and escape as such along with hot combustion gases. Hence a lesser amount of heat is available. So it is total amount of heat produced, when a unit mass / volume of a fuel has been burnt completely and the products of combustion are permitted to escape.

CandelaCandela (cd) is the SI base unit of luminous intensity.The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×1012 Hz and that has a radiant intensity in that direction of 1/683 watt per steradian.CapacitanceThe charge-storage ability of a capacitor, defined as the magnitude of charge stored on either plate divided by the applied voltage.

CarbanionThis is an abbreviation of "carbon anion", and is applied to negatively charged ions that are believed to occur during organic reactions. The carbanion then reacts with positive species to produce new products. To acquire a negative carbon ion it is necessary for the atom to retain two electrons forming a bond between itself and another group - see below:

R3C-H ⇌ R3C: + H

Carbon-Nitrogen-Oxygen CycleIn stars more massive than the sun (>1.1 Solar masses), this cycle is the primary process which converts hydrogen into helium. 12C serves as a catalyst, an ingredient which is necessary for the reaction but is not consumed. See also hot CNO Cycle

Carbonaceous biochemical oxygen demand (CBOD)The amount of oxygen required to oxidize any carbon containing matter present in a water.

CarbonylA functional group with an oxygen atom double bonded to a carbon atom.

ORAn organic compound containing the >CO group (see below). When a hydrogen atom is attached to the carbon, the resulting compound is known as an aldehyde. When only carbon atoms are attached, the resulting compound is known as a ketone. See also carboxyl group and amide group.

CarboxylAn organic compound containing the -COOH group (see below), Where a carbonyl group is attached to a hydroxyl group. See also carboxylic acids.

Carboxylic AcidCarboxylic acids are organic compounds characterized by the presence of one or more RC(=O)OH groups (the carboxyl group). In systematic chemical nomenclature carboxylic acids names end in the suffix -oic (e.g. ethanoic acids, CH3COOH). The carbon of the terminal group being counted as part of the chain. They are generally weak acids. Carboxylic acids include the large and important class of fatty acids and may be either saturated or unsaturated. There are also some natural aromatic carboxylic acids (benzoic, salicylic).

ORA substance containing the carboxyl group. The carboxylic hydrogen can be lost as a hydrogen ion, so these substances are also acidic. An example includes acetic acid.

Carburizing

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The process by which the surface carbon concentration of a ferrous alloy is increased by diffusion from the surrounding environment.

CarcinogenA substance capable of causing cancer in living organisms. It includes substances such as blue asbestos (crocidolite), which is a mineral, and benzene. Benzene has been used extensively for decades in chemistry and strict saftey guidlines must now be followed befrore it is used. Any new pharmaceutical, cosmetic or food chemical has to be checked to ensure that they are not carcinogenic.

Carnot CycleCarnot cycle is the most efficient cycle of operations for a reversible heat engine. Published in 1824 by N. L. S. Carnot (1796-1832), it consists of four operations on the working substance in the engine:

a) Isothermal expansion at thermodynamic temperature T1 with heat q1 taken in.b) Adiabatic expansion with a fall of temperature to T2.c) Isothermal compression at temperature T2 with heat q2 given out.d) Adiabatic compression at temperature back to T1.

According to the Carnot principle, the efficiency of any reversible heat engine depends only on the temperature range through which it works, rather than the properties of the working substances.

ORAn ideal heat engine (conceived by Sadi Carnot) in which the sequence of operations forming the working cycle consists of isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression back to its initial state.

CAS NumberChemical Abstracts System number; CAS® is the producer of the world's largest and most comprehensive databases of chemical information. It is a division of the American Chemical Society.

Cast IronA ferrous alloy with carbon content between 2 and 4.5 wt%.

CatabolismThe production of energy by the degradation of organic compounds.

CatalystA substance which aids or promotes a chemical reaction without forming part of the final product.

ORSubstance that speeds up a chemical process without actually changing the products of reaction

ORCatalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change. Catalyst that have the same phase as the reactants are homogenous catalysts (e.g. enzymes in biochemical reactions). Those that have a different phase are heterogeneous catalyst (e.g. metals or oxides used in gas reactions).

The catalyst provides an alternative pathway by which the reaction can proceed, in which the activation energy is lower. In thus increases the rate at which the reaction comes to equilibrium, although it does not alter the position of the equilibrium.

OR

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A substance that changes the rate at which a reaction equilibrium is attained, without itself being consumed. Catalysts can increase the rate of reaction (positive catalysts) or decrease them (negative catalysts or inhibitors).

Catalytic ConverterAn air pollution control device that removes organic contaminants by oxidizing them into carbon dioxide and water through a chemical reaction using a catalysis, which is a substance that increases (or decreases) the rate of a chemical reaction without being changed itself; required in all automobiles sold in the United State, and used in some types of heating appliances.

Catalytic CrackingThe process of breaking up heavier hydrocarbon molecules into lighter hydrocarbon fractions by use of heat and catalysts. The quality and yield of lighter hydrocarbon molecules produced by cracking can be greatly improved by using a suitable catalyst.

Catalytic ReformingReforming in the presence of a catalyst is called catalytic reforming. It gives better grade and yield of products as compared to thermal reforming.

CategoryA group of closely related chemicals whose physico-chemical, ecotoxicological or toxicological properties follow a regular pattern because of structural similarity.

CathodeElectrode where electrons are gained (reduction) in redox reactions.

ORCathode is a negative electrode of an electrolytic cell; to which positively charged ions (cations) migrate when a current is passed as in electroplating baths.In a primary or secondary cell (battery or accumulator) the cathode is the electrode that spontaneously becomes negative during discharge, and form which therefore electrons emerge.

In vacuum electronic devices, electrons are emitted by the cathode and flow to the anode.

Cathodic ProtectionA means of corrosion prevention whereby electrons are supplied to the structure to be protected from an external source such as anoother more reactive metal or a dc power supply.

CationA positively charged ion (Na+, H+).

ORCation is a positively charged atomic or molecular particle.

Cation ExchangeA cationic resin has positive ions built into its structure and therefore exchanges negative ions. In cation exchange, the side groups are ionized acidic groups, such as (-SO3H, -COOH, -OH) to which cations H+ are attached. The exchange reaction is one in which different cations in the solution displace the H+ from the solid.

Caustic SodaSee Sodium Hydroxide

Cavitation

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A method of making vapour-liquid emulsions by reduction of the hydrodynamic pressure within the to liquid to a value below the vapour pressure.

ORCavitation implies cavities or holes in the fluid we are pumping. These holes can also be described as bubbles, so cavitation is really about the formation of bubbles and their collapse. Bubbles form when ever liquid boils.

ORA suction pump sucks. That is, the pressure in its suction inlet is lowered. This causes a problem: if the pressure in the suction inlet drops below the vapour pressure of the liquid, vapour bubbles are free to form, because the pressure of the liquid is not enough to collapse them. This phenomenon is called cavitation. When these cavities form at the suction of the pump several things happen all at once.

We experience a loss in capacity. We can no longer build the same head (pressure) The efficiency drops. The cavities or bubbles will collapse when they pass into the higher regions of

pressure causing noise, vibration, and damage to many of the components. The cavities form for five basic reasons and it is common practice to lump all of them into the general classification of cavitation. This is an error because we will learn that to correct each of these conditions we must understand why they occur and how to fix them. Here they are in no particular order :

Vaporization Air ingestion Internal recirculation Flow turbulence The Vane Passing Syndrome

ORThe boiling of a liquid caused by a decrease in pressure rather than an increase in temperature.

CBODSee Carbonaceous biochemical oxygen demand

CellA unit of varying dimensions in a landfill which is isolated from the environment by 6 to 12 inches of soil cover. A cell is one day's waste or less. A cell is covered with soil at the end of each day.

CelsiusSee Centigrade

CementA substance that can be used to build together aggregates of sand or stone into a cohesive structure. May be a single compound or a mixture. May be hydraulic set, air set or chemical set.

CementiteIron carbide (Fe3C).

Center of GravityThe center of gravity of a body is that point in the body through which passes the resultant of weights of its component particles for all orientations of the body with respect to a uniform gravitational field. Also known as mass center.

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CentigradeA temperature scale defined by 0°C at the ice point and 100°C at boiling point of water at sea level. Also known as Celsius.

Central AtomIn a Lewis structure, usually the atom that is the most electronegative.

Centripetal ForceA force exerted on an object moving in a circular path which is exerted inward toward the center of rotation.

CeramicInorganic, nonmetalllic products for which the interatomic bonding is predominantly ionic.

ORCeramics are an inorganic material of very high melting point. Ceramics are metal silicates, oxides, nitrides, etc.

ORPolycrystalline ferroelectric materials which are used as the sensing units in piezoelectric accelerometers. There are many different grades, all of which can be made in various configurations to satisfy different design requirements.

Ceramic InsulationHigh-temperature compositions of metal oxides used to insulate a pair of thermocouple wires The most common are Alumina (Al2O3), Beryllia (BeO), and Magnesia (MgO). Their application depends upon temperature and type of thermocouple. High-purity alumina is required for platinum alloy thermocouples. Ceramic insulators are available as single and multihole tubes or as beads.

CermetA composite material consisting of a combination of ceramic and metallic materials.

Cetane NumberThe percentage by volume of cetane (Cetane number 100) in a blend with α-methylnaphthalene (cetane number 0); indicates the ability of fuel to ignite quickly after being injected into the cylinder of an engine.

ORA measure of a fuel's (liquid) ease of self-ignition.

CFCsSee Chlorofluorocarbons

CFMThe volumetric flow rate of a liquid or gas in cubic feet per minute.

CGS System of UnitsCgs system of units is a system of units based upon the centimeter, gram, and second. The International System (SI) has supplanted the cgs system.

Chain ReactionA reaction where the product of one step is a reactant in a later step, which produces a reactant for a later step, and so on.

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ChalcogensChalcogens are the Group 16 elements: oxygen (O), sulphur (S), selenium Se), tellurium (Te), and polonium (Po). Compounds of these elements are called chalcogenides.

CharcoalA material formed from the incomplete combustion or destructive distillation (carbonization) of organic material in a kiln or retort, and having a high energy density, being nearly pure carbon. (If produced from coal, it is coke.) Used for cooking, the manufacture of gunpowder and steel (notably in Brazil), as an absorbent and decolorizing agent, and in sugar refining and solvent recovery.

ChargeDescribes an object's ability to repel or attract other objects. Protons have positive charges while electrons have negative charges. Like charges repel each other while opposite charges, such as protons and electrons, attract one another.

Charle’s LawThe volume of a fixed mass of gas at constant pressure expand by constant fraction of its volume at 0 °C for each Celsius degree or kelvin its temperature is raised. For any ideal gas fraction is approximately 1/273. This can expressed by the equation

V = Vo [1 + (t/273)]were Vo is the volume at 0°C and V is its volume at t°C.This is equivalent to the statement that the volume of a fixed mass of gas at constant pressure is proportional to its thermodynamic temperature

V = kTThis law also know as Gay-Lussac's law.

An equation similar to that given above applies to pressures for ideal gases:P = Po [1 + (t/273)]

ChelateChelate is a compound characterized by the presence of bonds from two or more bonding sites within the same ligand to a central metal atom.

Chemical ChargesProcesses or events that have altered the fundamental structure of something.

Chemical Equations It show what reacts with what, what new substances are formed, and their reacting ratios.

ORAn expression of a fundamental change in the chemical substances.

ORChemical equation is a way of denoting a chemical reaction using the symbol for the participating particles (atoms, molecules, ions, etc.); for example,

aA + bB ⇄ cC + dDThe single arrow is used for an irreversible reaction; double arrows are used for reversible reactions. When reactions involve different phases it is usual to put the phase in brackets after the symbol.

s = solidl = liquidg = gasaq = aqueous

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The numbers a, b, c, and d, showing the relative numbers of molecules reacting, are called the stoichiometric coefficients. The convention is that stoichiometric coefficients positive for reactants and negative for products. If the sum of the coefficients is zero the equation is balanced.

Chemical fixation A term for several different methods of chemically immobilizing hazardous materials into a cement, plastic, or other matrix. Also known as chemicalor stabilization/solidification.

Chemical Formulas It show which elements are present and their ratios.

Chemical Oxygen DemandThe amount of oxygen required to oxidize any organic matter in the water using harsh chemical conditions.

Chemical PotentialFor a mixture of substances, the chemical potential of constituent B (μB) is defined as the partial derivative of the Gibbs energy G with respect to the amount (number of moles) of B, with temperature, pressure, and amounts of all other constituents held constant.

μB = ΔG/ΔnAlso called partial molar Gibbs energy. Components are in equilibrium if their chemical potentials are equal.

Chemical Properties These are such things as reactivity, oxidation states, flammability, and corrosiveness.

Chamical ReactionsA chemical process in which substances are changed into different substances with different properties.

Chemical RecyclingChemical recycling is the process of recycling waste products by partially altering their chemical structure.

Chemical Set CementA cement that sets through reaction or precipitation. Often subjected to a high temperature during manufacture or use.

Chemical SolidificationSee Chemical Fixation

Chemical StabilizationSee Chemical Fixation

Chemical SymbolsThese are the abbreviations for the elements.

ChemoautotrophicOrganisms which utilize inorganic carbon (carbon dioxide or carbonates) for synthesis and inorganic chemicals for energy. See autotrophic and photoautotrophic.ChemotrophOrganisms which obtain energy from the metabolism of chemicals, either organic or inorganic.

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ChiralMeans "handedness" - A chiral or asymmetric molecule is one which can be distinguished from its mirror image. An example includes lactic acid.

Chiral MoleculeChiral molecule is a molecule which cannot be superimposed on its mirror image. A common example is an organic molecule containing a carbon atom to which four different atoms or groups are attached. Such molecules exhibit optical activity, i.e., they rotate the plane of a polarized light beam.

ChlorofluorocarbonsChlorofluorocarbons, chemicals which result in a depletion of the ozone layer in the upper atmosphere.

ORSynthetic organic compounds used for refrigerants, aerosol propellants (prohibited in the U.S.), and blowing agents in plastic foams. CFCs migrate to the upper atmosphere destroying ozone and increasing global warming. Typical atmospheric residence times are 50 to 200 years.

ChromatographyChromatography is a process for separating mixtures such as gases into their component parts for analytical purposes.

ORChromatography is a method for separation of the components of a sample in which the components are distributed between two phases, one of which is stationary while the other moves. In gas chromatography, the gas moves over a liquid or solid stationary phase. In liquid chromatography, the liquid mixture moves through another liquid, a solid, or a gel. The mechanism of separation of components may be adsorption, differential solubility, ion-exchange, permeation, or other mechanisms.

ChromegaA chromium-nickel alloy which makes up the positive leg of type K and type E thermocouples (registered trademarks of OMEGA ENGINEERING, INC.).

Clapeyron EquationClapeyron equation is a relation between pressure and temperature of two phases of a pure substance that are in equilibrium,

(Dp/dT) = ΔtrsS/ ΔtrsVwhere ΔtrsS is the difference in entropy between the phases and ΔtrsV the corresponding difference in volume.

Clarifier (sedimentation basin)A tank in which quiescent settling occurs, allowing solid particles suspended in the water to agglomerate and settle to the bottom of the tank. The solids resulting from the settling being removed as a sludge.

ClimatologyThe study of the climate, how the earth's atmosphere performs over long periods of time.

ClosureA mathematical term which says that if you operated on any two real numbers A and B with +,-,* or /, you get a real number.

OR

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The act of preparing a landfill for long term inactivity, including placement of a cover over the landfill to prevent infiltration of surface water.

CNGSee Compressed Natural Gas

CoagulationParticle destabilization to enhance agglomeration.

CODSee Chemical Oxygen Demand

CokingIt is an operation in which the decomposition of bigger (higher boiling) hydrocarbon molecules into simpler, low boiling hydrocarbons of lower molecular weights takes place. Coking processes are more severe than cracking. The feedstock for the process is the residue of cracking process which may resist cracking by any means. Sometimes, coking is used because it is less expensive way to get more light distillates from a barrel of crude.Cold WorkingThe plastic deformation of a metal at a temperature below that at which it recrystallizes.

Colligative PropertyProperties of a solution that depend only on the number of particles dissolved in it, not the properties of the particles themselves. The main colligative properties addressed at this web site are boiling point elevation and freezing point depression.

ColloidColloidal systems are stable dispersions of microscopic solid particles.

ORSmall particles which have a negligible settling velocity. These particles have a very small mass so gravitational force is low compared to surface frictional forces. Typical colloidal sizes range from 10-3 mm to 1 mm.

ORColloids are systems in which there are two or more phases, with one (the dispersed phase) distributed in the other (the continuous phase). Moreover, at least one of the phases has small dimensions, in the range between 1 nanometer and 1 micrometer (10 -9 - 10-6 m). Dimension, rather than the nature of the material, is characteristic. In this size range, the surface area of the particle is large with respect to its volume so that unusual phenomena occur, e.g., the particles do not settle out of the suspension by gravity and are small enough to pass through filter membranes. Macromolecules (proteins and other high polymers) are at the lower limit of this range; the upper limit is usually taken to be the point at which the particles can be resolved in an optical microscope.

Colloidal particles may be gaseous, liquid, or solid, and occur in various types of suspensions:

Sols dispersions of small solid particles in a liquid.Emulsions colloidal systems in which the dispersed and continuous phases are

both liquids.Gels colloids in which both dispersed and continuous phases have a three-

dimensional network throughout the material.Aerosols colloidal dispersions of liquid or solid particles in a gas.Foams dispersions of gases in liquids or solids.

Colloid MillsColloid mills are machines used to grind aggregates into very fine particles or to apply very high shearing within a fluid to produce colloid suspensions or emulsions in which the particle sizes are less than 1 micrometer. One type of colloid mill is called a disc mill, in which a

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mixture of a solid and liquid (or two liquid) is passed between two discs a small distance apart, which rotate very rapidly relative to each other. Applications of colloid mills occur in food processing, in paint manufacture, and in the pharmaceutical industry. CombustionWhen substances combine with oxygen and release energy.

ORCombustion is the combination of a substance with oxygen in the presence of a flame accompanied by the production of heat and light. Combustion requires a supply of both fuel and oxygen (air) and can take place in the open atmosphere such as an open fire, or in a closed system, such as a car engine.

ORThe process of burning; the oxidation of a material by applying heat, which unites oxygen with a material or fuel.

Combustion ChamberThe volume of space at the top of the cylinder where burning of the air/fuel mixture begins.

Combustion GasesThe gaseous byproducts of the combustion of a fuel.

CommutativityA math property which states: A+B=B+A and A*B=B*A

CompensationAn addition of specific materials or devices to counteract a known error.

Compensating AlloysAlloys used to connect thermocouples to instrumentation. These alloys are selected to have similar thermal electric properties as the thermocouple alloys (however, only over a very limited temperature range).

ComplexationThe ionic bonding of one or more central ions or molecules by one or more surrounding ions or molecules.

ComponentA part of a mixture or solution.

CompositeA solid material made of two or more different substances, combined to produce a new substance whose properties are superior to the original components in a specific application.

ORA material brought about by combining materials differing in composition or form on a macroscale for the purpose of obtaining specific characteristics and properties. The constituents retain their identity such that they can be physically identified and they exhibit an interface between one another.

CompostingThe controlled aerobic degradation of organic wastes into a material which can be used for landscaping, landfill cover, or soil conditioning.Compound Two or more elements chemically combined forms a compound.

OR

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A compound (or molecule) is a combination of two or more different chemical elements (atoms) held together by chemical bonds.

ORTwo or more atoms joined together chemically, with covalent or ionic bonds.

ORA substance composed of two or more elements.

Compressed Natural GasNatural gas (methane) that has been compressed to a higher pressure gaseous state by a compressor; used in CNG vehicles.

CompressibilityCompressibility is the degree to which a fluid undergoes a reduction in volume under pressure. As a rule of thumb, compressibility is about 0.5% for each 1,000-psi pressure increase up to 4,000 psi.

Compression DistillationA distillation process in which the vapours from the still are subjected to compression. The vapours heated in this manner are then used to furnish heat to other units of equipment.

Compression settlingSettling which occurs in the lower reaches of clarifiers where particle concentrations are highest. Particles can settle only by compressing the mass of particles below.

CompressorA device used to compress air for mechanical or electrical power production, and in air conditioners, heat pumps, and refrigerators to pressurize the refrigerant and enabling it to flow through the system. Compressors are mechanical devices used to raise the pressure by lowering the volume. There are mainly two type of compressors :

Positive Displacement Compressors Dynamic Compressors

Positive Displacement Compressors – Reciprocating, Rotary Screw, and Rotary Vane compressor comes under this category.

Dynamic Compressor – Centrifugal, Axial-flow, and Diagonal or Mixed –flow compressors comes under this category.

Compressor - CentrifugalA centrifugal compressor compresses air or gas by means of mechanical rotating rotating vanes or impellers.

Compton ScatteringCollision process between a gamma ray and a bound atomic electron where only part of the gamma-ray energy is transferred to the electron. The probability for Compton scattering is approximately proportional to Z, and for energies greater than 500 keV approximately proportional to 1/Egamma

ConcentrationThe amount of substance in a specified space.

ORConcentration is the amount of given substance in a stated unit of a mixture, solution, or ore.

CA = nA/VThe concentration of an atom, ion, or molecule in a solution may be symbolized by the use of square brackets, as [Ca2+].ConcreteA composite material consisting of aggregate particles bound together in a solid body by a cement.

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CondensateThe liquid resulting when water vapour contacts a cool surface; also the liquid resulting when a vaporized working fluid (such as a refrigerant) is cooled or depressurized.

CondensationThe process by which water in air changes from a vapour to a liquid due to a change in temperature or pressure; occurs when water vapour reaches its dew point (condensation point); also used to express the existence of liquid water on a surface.

Condensation PolymerizationThe formation of polymers by an intermolecular reaction involving at least two monomer species, usually with the production of a low molecular weight by-product such as water.

Condensation ReactionThis is mainly an organic reaction where a simple molecule such as water or ammonia is eliminated when two molecules combine to produce another compound. A typical reaction is the esterification of an acid by an alcohol - in this case water is eliminated - see below:

Condensation reactions reaction play a major part in the polymer industry for the synthesis or artificial polymers.

CondenserThe device in an air conditioner or heat pump in which the refrigerant condenses from a gas to a liquid when it is depressurized or cooled.

ConductanceConductance or Thermal conduction is the quantity of heat passing through a quantity of material of unit thickness with unit heat flow area in unit time, when unit temperature difference is maintained across the opposite faces of material. It is denoted by k.

k = - Q.dx / A.dt (W.m / m2.K)(W / m.K) = (J / Sec.m.K)

ConductionThe conveying of electrical energy or heat through or by means of a conductor.

ORIt is the transfer of heat from one part of a body to the another part of the same body or from one body to another, which is in physical contact with it, without appreciable displacement of particles of the body. It mainly results from the motion of unbound electrons. It is restricted to flow of heat in solids only.

Conductivity (Thermal)See Thermal Conductivity

Conduction BandThe lowest-lying electron energy band that is not completely filled with electrons.

Confidence LevelThe range (with a specified value of uncertainty, usually expressed in percent) within which the true value of a measured quantity exists.

Congruent TransformationA transformation of one phase to another that does not involve any change in composition.

Conjugate Acid

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A substance which can lose a H+ ion to form a base.

Conjugate BaseA substance which can gain a H+ ion to form an acid.

ConstantanA copper-nickel alloy used as the negative lead in Type E, Type J, and Type T thermocouples.

ConsumersOrganisms which consume protoplasm produced from photosynthesis or consume organisms from higher levels which indirectly consume protoplasm from photosynthesis.

ContaminantAn impurity not intended to be present in the product that may be introduced through such things as poor cleaning, processing, lack of appropriate environmental and personnel controls during the manufacturing process, handling and distribution.

Continuous Stirred Tank ReactorThis may be thought of as a tank to which reactants flow in, and products flow out. In an ideal CSTR the contents of the reactor are uniformly distributed.

ConvectionThe circulatory motion that occurs in a fluid at a non-uniform temperature owing to the variation of its density and the action of gravity.

ORIt is the floe of heat that is resulted from the movement of fluid on a macroscopic scalein the form of circulating currents. It is classified as :

1) Free or Natural Convection2) Forced Convection

ORThe transfer of heat by means of air currents.

ConversionThe fraction of a species entering a system which is converted to product.

ORConversion is defined as the ratio of the amount of a reactant reacted (converted into product) to the amount of the same reactant fed initially.

Conversion ElectronAn alternate process to x-ray emission during the de-excitation of an excited atom.

Coordination NumberThe number of atomic or ionic nearest neighbors.

CoolantThe mixture of water and anti-freeze that picks up heat from the engine and transfers it to the air passing through the radiator. This transfer of heat keeps the engine operating within its optimum temperature rant preventing premature engine wear.

Cooling TowerA structure used to cool power plant water; water is pumped to the top of the tubular tower and sprayed out into the center, and is cooled by evaporation as it falls, and then is either recycled within the plant or is discharged.

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CopolymerA polymer that consists of two or more dissimilar mer units in combination along its molecular chains.

ORCopolymers are also known as heteropolymers. They made from two (or more) different monomers, which usually undergo a condensation reaction with the elimination of a simple molecule, such as ammonia or water. A typical example is the condensation of 1,6-diaminohexane (hexamethylenediamine) with hexanedioic acid (adipic acid) to form nylon 6,6.

The properties of a polymeric plastic can most easily be modified if it is a copolymer of two or more different monomers, e.g. acrylonitrile-butadiene-styrene copolymer (ABS). Varying the proportions of the component monomers can preselect its properties.

Coriolis ForceA result of centripetal force on a mass moving with a velocity radially outward in a rotating plane.

CorrosionDeteriorative loss of a metal as a result of dissolution environmental reactions.

Corrosive wasteA waste that is outside the pH range of 2 to 12.5 or a waste that corrodes steel at a rate greater than 6.35 mm (0.25 in) per year. One of EPA's four hazardous waste properties.

Cosmic RaysCosmic rays are high energy (1015 - 1017 eV) nuclear particles, electrons, and photons, originating mostly outside the solar system, which continually bombard the Earth's atmosphere.

Counterflow Heat ExchangerA heat exchanger in which two fluids flow in opposite directions for transfer heat energy from one to the other.

CoulombCoulomb (C) is the SI unit of electric charge. It is equal to the charge transferred by a current of one ampere in one second (C = A s). The unit is named after French physicist C. A. Coulomb (1736-1806).

ORA measurement of the quantity of electrical charge, usually expressed as pico coulomb (10-12 coulombs).

Coulomb’s LawCoulomb's law is the statement that the force F between two electrical charges q1 and q2

separated by a distance r isF = [1/4π εo].[q1q2/r2]

where εo is the permittivity of a vacuum, equal toε0 = 8.8542×10-12 F/m.

Covalent BondWhen two atoms share at least one pair of electrons.

ORA bond in which electrons are shared approximately equally by two atoms.

ORA primary inter-atomic bond that is formed by the sharing electrons between neighboring atoms.

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ORCovalent bond is a chemical bond between two atoms whose stability results from the sharing of two electrons, one from each atom.

CrackingCracking is defined as “the decomposition of bigger (higher boiling) hydrocarbon molecules into simpler, low boiling hydrocarbons of lower molecular weights.” There are two methods of cracking in use.

1) Thermal Cracking2) Catalytic Cracking

CreepThe time-dependent permanent deformation that occurs under stress; for most materials it is important only at elevated temperatures.

Critical Compression PressureThe highest possible pressure in a fuel-air mixture before spontaneous ignition occurs.

Critical MassCritical mass is the minimum mass of a fissionable material (235U or 239Pu) that will initiate an uncontrolled chain reaction as in an atomic bomb. The critical mass of pure 239Pu is about 4.5 kg, and of 235U about 15 kg.

Critical PointIn general, critical point is the point on the phase diagram of a two-phase system at which the two coexisting phases have identical properties and therefore represent a single phase. At the liquid-gas critical point of a pure substance, the distinction between liquid and gas vanishes, and the vapour pressure curve ends. The coordinates of this point are called the critical temperature and critical pressure. Above the critical temperature, it is not possible to liquefy the substance.

Critical PressureCritical pressure is the pressure of a fluid in its critical point; i.e. when it is at its critical temperature and critical volume.

Critical TemperatureCritical temperature is the temperature of the liquid-vapour critical point, that is, the temperature above which a gas cannot be liquefied by an increase of pressure.

Critical VolumeCritical volume is the volume of a fixed mass of a fluid at critical temperature and pressure.

CrosslinkingCross-linking is attachment of two chains of polymer molecules by bridges, composed of either an element, a group, or a compound, that join certain carbon atoms of the chains by primary chemical bonds, as indicated in the schematic diagramCross-linking occurs in nature in substances made up of polypeptide chains that are joined by the disulfide bonds of the cysteine residue, as in keratins or insulin. Cross-linking can be effected artificially, either adding a chemical substance (cross-linking agent), or by subjecting the polymer to high-energy radiation. Examples are: vulcanisation of rubber with sulphur, cross-linking of polystyrene with divinylbenzene, or cross-linking of polyethylene by means of high-energy radiation.Cross-linking has the effect of changing a plastic from thermoplastic to thermosetting. Thus, it also increases strength, heat and electrical resistance, and especially resistance to solvents and other chemicals.

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ORTo increase the rigidity and density of synthetic polymers groups are introduced into the monomer molecules which enable bonds to form between polymer chains - this is known as cross-linking. The degree of cross-likning can have a marked effect on the physical properties of the final product. An example are the silicones - they can vary from oils (low degree of cross-linking) to waxes (high degree of cross-linking).

Crosslinked PolymerA polymer in which adjacent linear molecular chains are joined at various positions by covalent bonds.

CrustCrust is the outer layer of the solid earth, above the Mohorovicic discontinuity. Its thickness averages about 35 km on the continents and about 7 km below the ocean floor.

Cryoscopic ConstantCryoscopic constant (Ef) is the constant that expresses the amount by which the freezing point Tf of a solvent is lowered by a non-dissociating solute, through the relation

ΔTf = Ef mwhere m is the molality of the solute.

CrystalA discrete solid where the atoms,ions or molecules are arranged in an ordered 3-dimensional structure. The regular structures have the ability to "bend" or diffract beams of X-rays, and this aspect of crystallography is an extremely helpful tool in structure determination.

Crystal StructureFor crystalline materials, the manner in which atoms or ions are arrayed in space. It is defined in terms of the unit cell geometry and the atom positions within the cell.

Crystal SystemA scheme by which crystal structures are classified according to unit cell geometry.

CrystallineThe state of a solid material characterized by a periodic and repeating three-dimensional arrays of atoms, ions, or molecules.

CrystallinityFor polymers, the state wherein a periodic and repeating atomic arrangement is achieved by molecular chain alignment.

CrystalliteA region within a crystalline polymer in which all the molecular chains are ordered and aligned.

CrystallizationCrystallization is a unit operation, that involves the separation of a solute from its solution in the form of crystals. It is the formation of solid particles within a homogenous phase.

CSTRSee Continuous Stirred Tank Reactor

Curie Temperature

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That temperature above which a ferromagnetic or ferrimagnetic material becomes paramagnetic.

ORFor a ferromagnetic material, Curie temperature or Curie point (TC) is the critical temperature above which the material becomes paramagnetic. For iron the Curie point is 760 °C and for nickel 356 °C. It is named after French physicist Pierre Curie (1859-1906).

ORThe temperature at which a normally magnetic material goes through a magnetic transformation and becomes non-magnetic.

CyberneticSystems which change in response to feedback.

Cyclic CompoundsA cyclic compound is one where the atoms are joined together so as to form a closed ring.

CycloalkanesCycloalkanes are cyclic saturated hydrocarbons containing a ring of carbon atoms joined by single bonds. They have the general formula CnH2n, for example cyclohexane, C6H12. In general, they behave like the alkanes but are rather less reactive.

DΔTlm

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See Log Mean Temperature Difference

Dalton’s LawIt states that the total pressure exerted by gaseous mixture is equal to the sum of the partial pressures of components of mixture. Mathematically, Dalton’s Law is equal to

P = pA + pB + pC + …where P is the total pressure exerted by the gaseous mixture and pA, pB, pC, …are the partial pressures of components A, B, C , …

Daughter IsotopeIn a nuclear equation the compound remaining after the parent isotope (the original isotope) has undergone decay. A compound undergoing decay, such as alpha decay, will break into an alpha particle and a daughter isotope.

DecayChange of an element into a different element, usually with some other particle(s) and energy emitted.

Decay Branching %The nuclide decay rate by a particular decay mode. Some nuclides decay by only one mode (100%), and others by more than one mode. For example, 187Pb decay by beta decay (98%) and alpha decay (2%).

Decay ModeDisappearance of a radioactive substance due to nuclear emission of an alpha or beta particle, capture of an atomic electron, neutrinos, spontaneous fission, and the emission of bremsstrahlung, x-rays, and conversion electrons. In rare instances proton, neutron, or light element (for example 14C) emission can occur. When a large amount of decay energy is available, beta-delayed emission of neutrons, protons, and other particles may occur.

Decay SchemeA drawing depicting the decay of a parent nucleus to a daughter nucleus. The betas or alphas are shown as arrows from the parent level to daughter level(s). Gamma rays de-exciting daughter levels are shown on the decay scheme.

DecimalThe number of digits to the right of the decimal point in a number

DecomposersOrganisms which utilize energy from wastes or dead organisms. Decomposers complete the cycle by returning nutrients to the soil or water and carbon dioxide to the air or water.

DecompositionWhere chemical compounds are broken up into simple molecules and even as far as their original elements. These processes are normally irreversible. An example of decomposition is when ammonium nitrate is heated. This produces nitrous oxide and water which are unable to recombine - see below:

NH4NO3 2H2O + N2O

Degree of PolymerizationDegree of polymerisation is the number of monomeric units in a macromolecule or an oligomer molecule.

DehumidifierA device that cools air by removing moisture from it.

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DenitrificationThe anoxic biological conversion of nitrate to nitrogen gas. It occurs naturally in surface waters low in oxygen, and it can be engineered in wastewater treatment systems.DenseA compact substance or a substance with a high density.

DensityIt is equal to mass/volume.

ORMass per unit volume of a substance.

ORIn the most common usage, density (ρ) is mass density or mass per unit volume.

ρ = m / VMore generally, the amount of some quantity (mass, charge, energy, etc.) divided by a length, area, or volume.

Relative density is the ratio of the density of a substance to the density of some reference substance. For liquids or solids, it is the ratio of the density (usually at 20 °C) to the density of water at 4 °C. This quantity was formerly called specific gravity.

DeoxygenationThe consumption of oxygen by the different aquatic organisms as they oxidized materials in the aquatic environment.

Destructive DistillationHeating complex substances to produce chemical changes in it, and distilling off the volatile substances so formed, eg. The destructive distillation of coal to produce coal-gas and many other valuable products.

Detergents(CH2)11O.SO2.ONa they were superseded by alkyl benzene sulphonates but these could not be broken down easily by bacteria at sewage works so these were eventually replaced by more eco-friendly detergents. Detergent molecules come in two parts - the sulphate or phosphate end (water soluble hydrophilic portion) and an organic hydrocarbon chain (water insoluble hydrophobic portion).

ORThese are organic chemicals designed to clean surfaces or objects. They do this by reducing the surface tension and suspend dirt in suspension from the object to be cleaned. Early detergents were long chain alcohol derivatives of sodium sulphate salts, such as sodium lauryl sulphate CH3

ORThese are the substances used to enhance the cleaning action. These are surface-active compounds, either natural or synthetic. Oil soluble detergents are used in gasoline and lubricating oils to hold particulate impurities in suspension. Among the water-soluble detergents, alcohols and common soaps are effective. Still more so are the synthetic types (syndets) such as sulphonated dodecyclobenzene and similar alkylates. The liniar alkylate sulphonates (LAS) are more biodegradable than are the branched-chain type, they are made from petrochemicalsby various cracking and polymerization techniques. Phosphatic compounds called builders promote detergent action. These pollutants are generally regarded as enemies of clean water, are still highly popular in homes and industries alike. Basically, detergents lower the surface tension of wash water, make the water more wettable, emulsify oils and greases break up colloids cause floatation and create lather or foam. At the same time they utterly destroy useful bacteria and organisms. Moreover, detergents containing phosphate can contribute to accelerate algae growth and other forms of enrichment of receiving waters. Three general types of detergents in use today are :

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1) Anionic detergents2) Cationic detergents

& 3) non-ionic detergents

DevitrificationThe process in which a glass (noncrystalline or vitreous solid) transforms to a crystalline solid

Dew Point Upon cooling a vapour mixture, this is the point at which droplets of liquid first appear.

ORThe temperature to which air must be cooled, at constant pressure and water vapour content, in order for saturation or condensation to occur; the temperature at which the saturation pressure is the same as the existing vapour pressure; also called saturation point.

DiamagnetismA weak form of induced or nonpermanent magnetism for which the magnetic susceptibility is negative.

ORIn diamagnetism the magnetization is in the opposite direction to that of applied field, i.e. susceptibility is negative. It results from changes induced in the orbits of electrons in the atoms of a substance by the applied field, the direction of the change opposing the applied flux.

Diazo CompoundsThis is a series of organic compounds possessing the general formula Ar-N=N-Y, where Ar is an aromatic group and Y is any group linked to the nitrogen except via a carbon atom. They are different from the azo compounds which have the general formula Ar-N=N-Ar'. Diazo compounds are formed from amines by a two stage diazotisation reaction. Stage one is the conversion of an aromatic amine into a diazonium chloride salt using cold sodium

nitrite and hydrochloric acid - see below:The second stage is the reaction of the diazonium chloride salt with an appropriate

compound - such as another aromatic amine, eg. the reaction with p-toluidine - see below:

ORDiazo compounds are compounds having the divalent diazo group, =N+=N-, attached to a carbon atom. The term includes azo compounds, diazonium compounds, and also such compounds as diazomethane, CH2=N2.

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DielectricAny material that is electrically insulating.

Dielectric ConstantThe ratio of the permittivity of a medium to that of a vacuum.

ORDielectric constant or permittivity (ε) is an index of the ability of a substance to attenuate the transmission of an electrostatic force from one charged body to another. The lower the value, the greater the attenuation. The standard measurement apparatus utilizes a vacuum whose dielectric constant is 1. In reference to this, various materials interposed between the charged terminal have the following value at 20 °C:

air 1.00058 benzene 2.3 glass 3acetic acid 6.2 ammonia 15.5 ethanol 25glycerol 56 water 81

The exceptionally high value for water accounts for its unique behaviour as a solvent and in electrolytic solutions. Dielectric constant values decrease as the temperature rises.

Dielectric StrengthThe magnitude of an electric field necessary to cause significant current passage through a dielectric material.

DienesDienes are unsaturated organic compounds that contain two fixed double bonds between carbon atoms. Dienes in which the two double-bond units are linked by one single bond are termed conjugated.

DieselDiesel oil is a fraction obtained between 150 - 400°C during distillation operation. It is a mixture of paraffinic, naphthenic, olefinic and aromatic hydrocarbons having 12 to 18 carbon atoms. Its approx. composition is C – 84 %, H – 16 % and less than 0.1 % S. Two grades of diesel, namely High Speed Diesel Oil (HSD) and Light Diesel Oil (LDO) are in use. HSD is widely used in diesel engines for automotive purposes, as in buses, trucks, and other diesel locomotives. On the other hand, stationary and marine diesel engines, as installed in ships or used for electricity generation consume LDO.

DiffusionMass transport by atomic motion.

ORDiffusion is the spontaneous mixing of one substance with another when in contact or separated by a permeable membrane. Diffusion is a result of the random motions of their component atoms, molecules, ions, or other particles. Diffusion occurs most readily in gases, less so in liquids, and least in solids. The rate of diffusion is proportional to the concentration of the substance and increases with temperature. The theoretical principles are stated in Fick's laws.

ORThe movement of individual molecules through a material; permeation of water vapour through a material.

Diffusion CoefficientThe constant of proportionality between diffusion flux and the concentration gradient in Fick's first law.

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Dioxins (PCDDs)General name given to 210 organic compounds containing carbon, oxygen and hydrogen with one to eight chlorine atoms.

Dipole (Electric)A pair of equal yet opposite electrical charges that are separated by a small distance

ORDipole is a pair of separated opposite electric charges. Electric dipole is an assemblage of atoms or subatomic particles having equal electric charges of opposite sign separated by a finite distance. In the case of HCl, the electrons are attracted towards the more electronegative chlorine atom.Dipole-Dipole ForcesIntermolecular forces that exist between polar molecules. Active only when the molecules are close together. The strengths of intermolecular attractions increase when polarity increases.

Dipole MomentElectric dipole moment (μ) is the product of the positive charge and the distance between the charges. Dipole moments are often stated in debyes; The SI unit is the coulomb metre. In a diatomic molecule, such as HCl, the dipole moment is a measure of the polar nature of the bond; i.e. the extent to which the average electron charges is displaced towards one atom (in the case of HCl, the electrons are attracted towards the more electronegative chlorine atom). In a polyatomic molecule, the dipole moment is the vector sum of the dipole moments of the individual bonds. In a symmetrical molecule, such as tetrafluoromethane (CF4) there is no overall dipole moment, although the individual C-F bonds are polar.

DisaccharidesDisaccharides are compounds in which two monosaccharides are joined by a glycosidic bond. For example, sucrose comprises one glucose molecule and one fructose molecule bonded together.

Discrete SettlingSettling in which individual particles settle independently, neither agglomerating or interfering with the settling of the other particles present. This occurs in waters with a low concentration of particles.

DisinfectionThe destruction or inactivation of pathogenic microorganisms. See sterilization.

DislocationA linear crystalline defect around which there is an atomic misalignment.

DispersionA stable mixture of particles suspended in a fluid medium.

Dispersion ForcesDispersion is an intermolecular attraction force that exists between all molecules. These forces are the result of the movement of electrons which cause slight polar moments. Dispersion forces are generally very weak but as the molecular weight increases so does their strength.

DissociationBreaking down of a compound into its components.

OR

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Dissociation is the process by which a chemical combination breaks up into simpler constituents as a result of either added energy (dissociated by heat), or the effect of a solvent on a dissolved polar compound (electrolytic dissociation). It may occur in the gaseous, solid, or liquid state, or in solution.An example of dissociation is the reversible reaction of hydrogen iodide at high temperatures

2HI(g) ⇌ H2(g) + I2(g)The term dissociation is also applied to ionisation reactions of acids and bases in water. For example

HCN + H2O ⇌ H2O+ + CN-

which is often regarded as a straightforward dissociation into ionsHCN ⇌ H+ + CN-

Dissociation ConstantDissociation constant is a constant whose numerical value depends on the equilibrium between the undissociated and dissociated forms of a molecule. A higher value indicates greater dissociation.

The term dissociation is also applied to ionisation reactions of acids and bases in water. For example

HCN + H2O ⇌ H2O+ + CN-

which is often regarded as a straightforward dissociation into ionsHCN ⇌ H+ + CN-

The equilibrium constant of such a dissociation is called the acid dissociation constant or acidity constant, given by

Ka = [H+ ].[ CN-] / [HCN]The concentration of water [H2O] can be taken as constant.Similarly, for a base, the equilibrium

NH3 ⇌ NH4+ + OH-

is also a dissociation; with the base dissociation constant or basicity constant, given byKa = [NH4

+ ].[ OH-] / [NH3]Ka (Kb) is a measure of the strength of the acid (base).

Dissolved OxygenThe amount of molecular oxygen dissolved in water.

DistillateThe liquid obtained through distillation.

DistillationThe process of boiling a liquid and collecting its condensed vapour. This process is used to purify liquids and to separate liquid mixtures.

ORThe separation and purification of a mixture of components by vapourisation followed by condensation, based on the different volatilities of each component.

ORDistillation is the process of boiling a liquid and condensing and collecting the vapour. The liquid collected is the distillate. The usual purpose of distillation is purification or separation of the components of a mixture. This is possible because the composition of the vapour is usually different from that of liquid mixture from which it is obtained. Gasoline, kerosene, fuel oil, and lubricating oil are produced from petroleum by distillation.

ORIt is an operation in which constituents of a liquid mixture (solution) are separated using thermal energy. Basically the difference in vapour pressure of different constituents at the same temperature is responsible for such separation. This unit operation is also termed as fractional distillation or fractionation.

Two types of distillation operations are carried out in refineries :1) Atmospheric Distillation

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And 2) Vacuum Distillation

Distillation – AtmosphericSee Atmospheric Distillation

Distillation – AzeotropicSee Azeotropic Distillation

Distillation – CompressionSee Compression Distillation

Distillation – DestructiveSee Destructive Distillation

Distillation – FractionalSee Fractional Distillation

Distillation – SteamSee Steam Distillation

Distillation – VacuumSee Vacuum Distillation

DistributivityA math property which states: A*(B+C)=(A*B)+(A*C)

DOSee Dissolved Oxygen

DopingThe intentional alloying of semiconducting materials with controlled concentrations of donor or acceptor impurities.

Double BondWhen an atom is bonded to another atom by two sets of electron pairs.

DraftA column of burning combustion gases that are so hot and strong that the heat is lost up the chimney before it can be transferred to the house. A draft brings air to the fire to help keep it burning.

DragResistance caused by friction in the direction opposite to that of movement (i.e., motion) of components such as wind turbine blades.

DrawingA deformation technique used to fabricate metal wire and tubing. Deformation is accomplished by pulling the material through a die by means of a tensile force applied on the exit side.

DriftA change of a reading or a set point value over long periods due to several factors including change in ambient temperature, time, and line voltage.

Driving Force

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When two phases are brought into intimate contact, the phases will tend to approach equilibrium due to tendency for change to take place. The difference between the existing condition and the equilibrium condition is called the driving force, which causes the change.Eg.- Concentration difference is the driving force for mass transfer analogous to temperature difference for heat transfer.

DrugAny chemical compound used for medicianal purposes can be considered a drug. There are naturally occuring substances such as ethanol and caffeine as well as synthetic drugs such as aspirin and amphetamines. In general the term "drug" is used for compounds that can cause addiction with emphasis on narcotics.

Dry Bulb TemperatureThe temperature of the air as measured by a standard thermometer.

DuctilityA measure of a material's ability to undergo appreciable plastic deformation before fracture.

DumpAn illegal and uncontrolled area where wastes have been placed on or in the ground. See Landfill.

DyesDyes are chemical compounds that can attach themselves to fabrics or surfaces to give them colour. Most dyes are complex organic molecules and need to be resistant to many things such as the weather and the action of detergents. Indigo, otained from plants was being used by the Egyptians 5000 years ago, and natural dyes obtained from plants and animal sources are stil used today. In 1856, Perkin developed the first synthetic dye based upon aniline.

Dynamic ViscositySee Viscosity

Dynamic PressureThe difference in pressure levels from static pressure to stagnation pressure caused by an increase in velocity. Dynamic pressure increases by the square of the velocity.

DyneThe absolute centimeter-gram-second unit of force; that force that will impart to a free mass of one gram an acceleration of one centimeter per second per second.

EE = mc2

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Where: e is energy, m is mass, and c is the speed of light. Einstein's famous equation describes how energy and mass are related. In our animated decays, mass is lost. That mass is converted into energy in the form of electromagnetic waves. Because the speed of light is so great, a little matter can transform into large amount of energy.

Ebullioscopic ConstantEbullioscopic constant (Eb) is the constant that expresses the amount by which the boiling point Tb of a solvent is raised by a nondissociating solute, through the relation

ΔTb = Eb bwhere b is the molality of the solute.

EcologyThe study of living organisms and their environment or habitat.

EcosystemAn organism or group of organisms and their surroundings. The boundary of an ecosystem may be arbitrarily chosen to suit the area of interest or study.

EfficiencyUnder the First Law of Thermodynamics, efficiency is the ratio of work or energy output to work or energy input, and cannot exceed 100 percent. Efficiency under the Second Law of Thermodynamics is determined by the ratio of the theoretical minimum energy that is required to accomplish a task relative to the energy actually consumed to accomplish the task. Generally, the measured efficiency of a device, as defined by the First Law, will be higher than that defined by the Second Law.

EffluentThe fluid exiting a system, process, tank, etc. An effluent from one process can be an influent to another process. See influent.

Effluent based standardsStandards which set concentration or mass per time limits on the effluent being discharged to a receiving water.

EffusionMovement of gas molecules through a small opening.

Elastic ModulusSee Modulus of Elasticity

ElastomerA polymeric material that may experience large and reversible elastic deformations.

Electrical ResistivityElectrical resistivity (ρ) is electric field strength divided by current density when there is no electromotive force in the conductor. Resistivity is an intrinsic property of a material. For a conductor of uniform cross section with area A and length L, and whose resistance is R, the resistivity is given by

ρ = R(A/l)The SI unit is Ω m.Electrochemical CellGives an electric current with a steady voltage as a result of an electron transfer reaction.

Electrochemical Series

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Electrochemical series is a series of chemical elements arranged in order of their standard electrode potentials. The hydrogen electrode

H+(aq) + e- ⇌ 1/2H2(g)is taken as having zero electrode potential. An electrode potential is, by definition, a reduction potential.

Elements that have a greater tendency than hydrogen to lose electrons to their solution are taken as electropositive; those that gain electrons from their solution are below hydrogen in the series and are called electronegative.

The series shows the order in which metals replace one another from their salts; electropositive metals will replace hydrogen from acids.

Electrode PotentialElectrode potential is defined as the potential of a cell consisting of the electrode in question acting as a cathode and the standard hydrogen electrode acting as an anode. Reduction always takes place at the cathode, and oxidation at the anode. According to the IUPAC convention, the term electrode potential is reserved exclusively to describe half-reactions written as reductions. The sign of the half-cell in question determines the sign of an electrode potential when it is coupled to a standard hydrogen electrode.Electrode potential is defined by measuring the potential relative to a standard hydrogen half cell

H2(g) ⇌ 2H+(aq) + 2e-

The convention is to designate the cell so that the oxidized form is written first. For examplePt(s)|H2(g)|H+(aq)||Zn2+(aq)|Zn(s)

The e.m.f. of this cell ise.m.f. = Eright - Eleft

By convention, at p(H2) = 101325 Pa and a(H+) = 1.00, the potential of the standard hydrogen electrode is 0.000 V at all temperatures. As a consequence of this definition, any potential developed in a galvanic cell consisting of a standard hydrogen electrode and some other electrode is attributed entirely to the other electrode

e.m.f. = E(Zn2+/Zn)

ElectrodesDevice that moves electrons into or out of a solution by conduction.

ElectrolysisChanging the chemical structure of a compound using electrical energy.

ORElectrolysis is the decomposition of a substance as a result of passing an electric current between two electrodes immersed in the sample.

Electrolyte Any solution that conducts an electrical current, such as a mixture of sulfuric acid and distilled water found in automotive batteries.

ORA nonmetallic (liquid or solid) conductor that carries current by the movement of ions (instead of electrons) with the liberation of matter at the electrodes of an electrochemical cell.

Electromagnetic SpectrumComplete range of wavelengths which light can have. These include infared, ultraviolet, and all other types of electromagnetic radiation, as well as visible light. Electromotive ForceElectromotive force (e.m.f. or EMF) is the difference in electric potential that exists between two dissimilar electrodes immersed in the same electrolyte or otherwise connected by ionic conductors.

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ElectronIt is the basic particle whose charge is -1 and whose mass is 1/1837 g/mol (amu).

OROne of the parts of the atom having a negative charge. Indivisible particle with a charge of -1.

ORAn elementary negatively charged particle orbiting within an atom, the electrons are arranged in shells - and it is the outermost shell electrons which take part in bond formation.

ORElectron is discovered by J.J. Thompson (1856-1940) in 1896. The electron is an elementary particle with a negative electric charge of (1.602 189 2 ± 0.000 004 6) × 10 -19 C and a mass of 1/1837 that of a proton, equivalent to (9.109 534 ± 0.000 047) × 10-31 kg. Electrons are arranged in from one to seven shells around the nucleus; the maximum number of electrons in each shell is strictly limited by the laws of physics (2n2). The outer shells are not always filled: sodium has two electrons in the first shell (2×12 = 2), eight in the second (2×22 = 8), and only one in the third (2×32 = 18). A single electron in the outer shell may be attracted into an incomplete shell of another element, leaving the original atom with a net positive charge. Valence electrons are those that can be captured by or shared with another atom.Electrons can be removed from the atoms by heat, light, electric energy, or bombardment with high-energy particles. Decaying radioactive nuclei spontaneously emits free electrons, called β particles.

ORAn elementary particle with a unit electrical charge and a mass 1/1837 of the proton. Electrons surround the atom's positively charged nucleus and determine the atom's chemical properties.

Electron AffinityElectron affinity (EA) is the energy change occurring when an atom or molecule gains an electron to form a negative ion. For an atom or molecule X, it is the energy released for the electron-attachment reaction

X(g) + e- ⇌ X- (g)Often this is measured in electronvolts. Alternatively, the molar enthalpy change, ΔH, can be used.

Electron Capture DecayNuclear decay by capture of an atomic electron. If the decay energy is greater than 1022 keV, positron emission can also occur in competition with electron capture.

Electron GeometryStructure of a compound based on the arrangement of its electrons.

Electron PairTwo electrons within one orbital with opposite spins responsible for a chemical bond. See also lone pair.

Electron RadiationRadiation consisting of electric and magnetic waves that travel at the speed of light. Examples: light, radio waves, gamma rays, x-rays.

Electron SpinElectron spin (s) is the quantum number, equal to 1/2, that specifies the intrinsic angular momentum of the electron.

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Electron VoltElectron volt (eV) is a non-SI unit of energy used in atomic and nuclear physics, equal to approximately 1.602177 × 10-19 J. The electron volt is defined as the kinetic energy acquired by an electron upon acceleration through a potential difference of 1 V.

ElectronegetivityMeasure of a substances's ability to attract electrons.

ORThe potential of an atom to attract electrons when the atom is bonded in a compound. The scale is 0 to 4 with 0 being the most electropositive (low attraction) and 4 being the most electronegative (high attraction).

ORfor an atom, having a tendency to accept valence electrons.

ORElectronegativity is a parameter originally introduced by L. Pauling which describes, on a relative basis, the power of an atom to attract electrons. For example, in hydrogen chloride, the chlorine atom is more electronegative than the hydrogen and the molecule is polar, with negative charge on the chlorine atom.

There are various ways of assigning values for the electronegativity of an element. Pauling electronegativities are based on bond dissociation energies using a scale in which fluorine, the most electronegative element, has value 4 and francium, the lowest electronegative element, has value 0.7.

ElectrophoresisElectrophoresis is a technique for the analysis and separation of colloids, based on the movement of charged colloidal particles in an electric field. The migration is toward electrodes of charge opposite to that of the particles. The rate of migration of the particles depends on the field, the charge on the particles, and on other factors, such as the size and shape of the particles.

Electrophoresis is important in the study of proteins. The acidity of the solution can be used to control the direction in which a protein moves upon electrophoresis.

Electrostatic ForcesForces between charged objects.

Electrostatic PrecipitatorA device which uses an electric field to trap particulate pollutants.

ElementIt is the simplest form of matter.

ORSubstance consisting of only one type of atom.

Elementary ReactionA reaction in which the rate expression corresponds to the stoichiometric equation.

EmissivityThe ratio of the radiant energy (heat) leaving (being emitted by) a surface to that of a black body at the same temperature and with the same area; expressed as a number between 0 and 1.

ORThe ratio of total emissive power E of a body to that of the black body Eb at the same temperature.

Empirical Formula

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It is the simplest whole number ratio of elements in a compound, ie CH2.OR

Formula showing the simplist ratio of elements in a compound.

EmulsifierAn emulsifier (or emulsifying agent) is a substance which can be used to produce an emulsion out of two liquids that normally cannot be mixed together (such as oil and water). Emulsifiers are common in foods to maintain consistency within puddings, powders, etc.

EmulsionA dispersal, with a variety of industrial uses of one liquid as small particles in another liquid. An example would be milk.

OREmulsion is colloidal system in which the dispersed and continuous phases are both liquids (e.g. oil in water or water in oil). Such systems require an emulsifying agent to stabilize the dispersed particles.

EnantiomersEnantiomers are a chiral molecule and its non-superposable mirror image. The two forms rotate the plane of polarized light by equal amounts in opposite directions. Also called optical isomers.

EnergyEnergy (E, U) is the characteristic of a system that enables it to do work. Like work itself, it is measured in joules (J).

The internal energy of a body is the sum of the potential energy and the kinetic energy of its component atoms and molecules.

Potential energy is the energy stored in a body or system as a consequence of its position, shape, or state (this includes gravitational energy, electrical energy, nuclear energy, and chemical energy).

Kinetic energy is energy of motion and is usually defined as the work that will be done by body possessing the energy when it is brought to rest. For a body of mass m having a speed v, the kinetic energy is mv2/2. Kinetic energy is most clearly exhibited in gases, in which molecules have much greater freedom of motion than in liquids and solids.

ORAbility to do work.

Energy ScaleThe energy scale used by most nuclear scientists is electron volts (eV), thousands of electron volts (keV), and millions of electron volts (MeV). An electron volt is the energy acquired when an electron falls through a potential difference of 1 volt. 1 eV=1.602*1012ergs. Masses are also given by their "mass-equivalent" energy (E=mc2). The mass of the proton is 938.27231 MeV.

Endothermic ReactionIt takes more energy to start it than it gives back. It has a positive DH. It needs energy to keep it going. An example is cooking. (Chippers a baking)

ORReaction that absorbs heat from its surroundings as the reaction proceeds.

ORA heat absorbing reaction or a reaction that requires heat.EnergyAbility to do work.

Engineering Ceramics

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Technical ceramics for structural applications.

ENSDFThe Evaluated Nuclear Structure Data File is evaluated by an international collaboration of nuclear scientists. ENSDF is a database of nuclear structure and decay data.

EnthalpyIt is the heat of reaction, either exo- or endothermic. It is measured either in kilocalories/mole or kilojoules/mole.

ORChange in heat.

OREnthalpy (H) is a thermodynamic property of a system defined by

H = U + pVwhere U is the internal energy of the system, p its pressure, and V its volume. J.W. Gibbs put the concept of an ensemble forward in 1902. In a chemical reaction carried out in the atmosphere the pressure remains constant and the enthalpy of reaction (ΔH), is to equal

ΔH = ΔU + pΔVFor an exothermic reaction ΔH is taken to be negative.

EntropyMeasure of the disorder of a system.

OREntropy (S) is a measure of the unavailability of a system's energy to do work; in a closed system, an increase in entropy is accompanied by a decrease in energy availability. When a system undergoes a reversible change the entropy (S) changes by an amount equal to the energy (Q) transferred to the system by heat divided by the thermodynamic temperature (T) at which this occurs.

ΔS = (ΔQ/T)All real processes are to a certain extent irreversible changes and in any closed system an irreversible change is always accompanied by an increase in entropy.

ORA measure of the unavailable or unusable energy in a system; energy that cannot be converted to another form.

EnzymeA naturally occuring protein that fascilitates a specific biochemical reaction; a biological catayst.

OREnzyme is a protein that acts as a catalyst in biochemical reactions. Each enzyme is specific to a particular reaction or group of similar reactions. Many require the association of certain nonprotein cofactors in order to function. The molecule undergoing reaction (the substrate) binds to a specific active site on the enzyme molecule to form a short-lived intermediate: this greatly increases (by a factor of up to 1020) the rate at which the reaction proceeds to form the product.

EpilimnionThe top layer of a lake.

Epoxy ResinEpoxy resins are thermosetting resins produced by copolymerising epoxide compounds with phenols (e.g. epichlorohydrin and bisphenol A). They contain ether linkages (-O-) and form a tight, cross-linked polymer network. Toughness, good adhesion, corrosive-chemical

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resistance, and good dielectric properties characterize epoxy resins. Most epoxy resins are two-part type which harden when blended.

Equation of StateEquation of state is an equation relating the pressure, volume, and temperature of a substance or system. Equation of state for ideal gas

pV = nRTwhere p is pressure, V molar volume, T temperature, and R the molar gas constant (8.314 JK-1mol-1).

EquilibriumWhen the reactants and products are in a constant ratio. The forward reaction and the reverse reactions occur at the same rate when a system is in equilibrium.

ORA state of balance in terms of molecular concentration of compounds undergoing a reversible reaction. Equilibrium exists when the rate of both the reactions (forward and backward) are equal at a given temperature.

ORWhen, for any reversible reaction, at a constant temperature, if the rate of forward reaction is as same as that of backward reaction, a state of balance in terms of molecular concentration of compounds is achieved, that is known as equilibrium.

Equilibrium ConstantValue that expresses how far the reaction proceeds before reaching equilibrium. A small number means that the equilibrium is towards the reactants side while a large number means that the equilibrium is towards the products side.

Equilibrium ExpressionThe expression giving the ratio between the products and reactants. The equilibrium expression is equal to the concentration of each product raised to its coefficient in a balanced chemical equation and multiplied together, divided by the concentrat ion of the product of reactants to the power of their coefficients.

EquivalentThe mass of the compound which will produce one mole of available reacting substance. Thus, for an acid, this would be the mass of acid which will produce one mole of H+, for a base, one mole of OH-.

Equivalence PointOccurs when the moles of acid equal the moles of base in a solution.

Equivalent ConductanceEquivalent conductance of an electrolyte is defined as the conductance of a volume of solution containing one equivalent weight of dissolved substances when placed between two parallel electrodes 1 cm apart, and large enough to contain between them all of the solution. l is never determined directly, but is calculated from the specific conductance (Ls). If C is the concentration of a solution in gram equivalents per liter, then the concentration of a solution in gram equivalents per liter, then the concentration per cubic centimeter is C/1000, and the volume containing one equivalent of the solute, is, therefore, 1000/C.

ErgErg (erg) is a non-SI (cgs) unit of energy, equal to 10-7 J.

ORA unit of work done by the force of one dyne acting through a distance of one centimeter.

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EsterAny of a class of organic compounds made from the chemical reaction between an alcohol and an organic acid.

ORA volatile fruity odoured product of the reaction between a carboxylic acid and an alcohol.

OREsters are organic compounds formed by reaction between alcohol and acids. Esters formed from carboxylic acids have the general formula RCOOR'. Triesters, molecules containing three ester groups, occur in nature as oils and fats

ETBESee Ethylene Tertiary Butyl Ether

EthersAn organic compound which has two hydrocarbon groups bound by an interior oxygen atom. The general formula is R'-O-R".

OREthers are organic compounds with formula R-O-R, where R is not equal to H. They may be derived from alcohols by elimination of water, but the major method is catalytic hydration of olefins. They are volatile highly flammable compounds; when containing peroxides they can detonate on heating. The term ether is often used synonymously with ethyl ether.

Ethylene Tertiary Butyl EtherA chemical compound produced in a reaction between ethanol and isobutylene (a petroleum-derived by-product of the refining process). ETBE has characteristics superior to other ethers: low volatility, low water solubility, high octane value, and a large reduction in carbon monoxide and hydrocarbon emissions.

Eucaryotic OrganismsOrganisms which possess a nuclear membrane. This includes all known organisms except viruses and bacteria.

Euler NumberEuler number (Eu) is a dimensionless quantity used in fluid mechanics, defined by

Eu = ΔP/(ρv2)where p is pressure, ρ is density, and v is velocity.

European chemicals legislationMainly based on four legal instruments on chemicals currently in force in the Community : ·

EutecticEutectic is a solid solution consisting of two or more substances and having the lowest freezing point of any possible mixture of these components.

Eutectic point is the lowest temperature at which the eutectic mixture can exist in liquid phase. A liquid having the eutectic composition will freeze at a single temperature without change of composition.

ORA mixture of substances that has a melting point lower than that of any mixture of the same substances in other proportions.

Eutectic PhaseOne of the two phases found in the eutectic structure.

Evaporation

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The conversion of liquid water to water vapour. It occurs on the surface of water bodies such as lakes and rivers and immediately after precipitation events in small depressions and other storage areas.

EvapotranspirationThe sum of evaporation and transpiration. Since it is difficult to measure the two terms independently, they are often grouped as one value.

ExcipientAny substances other than the active drug or product which have been appropriately evaluated for safety and are included in a drug delivery system.

Exothermic ReactionIt gives out more energy than was put in to start the reaction. It has a negative DH. It keeps going after it is started. An example is a fire.

ORReaction that gives off heat to the environment.

ORThe majority of chemical reactions are accompanied by the evolution of heat - these is known as exothermic reactions. The reaction between an acid and a base is exothermic, it is possible to feel the temperature change when one is added to the other - see below:

HCl + NaOH NaCl + H2OA rapid exothermic reation results in an explosion, as occurs when TNT explodes.

ORA process is said to be exothermic when it releases heat.

ORA reaction or process that produces heat; a combustion reaction.

ExponentiationRaising something to a power.

Extinguishing AgentsMedia suitable for controlling or putting out a fire, when properly applied.

ExtractionExtraction is the technique, used for the separation of two or more miscible liquids by the use of a solvent that preferentially dissolves one of them. When the separation by distillation is ineffective or very difficult, extraction is one of the main alternative to consider. Close boiling mixtures or substances, that cannot withstand the temperature of distillation, even under a vacuum, may often be separated from impurities by extraction, which utilizes chemical differences instead of vapor pressure difference.

Extrinsic SemiconductorA semi-conducting material for hich the electrical behavior is determined by impurities.

ExtrusionA forming technique whereby a material is forced, by compression, through a die orifice.

F

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Face-Centered CubicA crystal structure found in some of the common elemental metals. Within the cubic unit cell, atoms are located at all corner and face-centered positions.

FacultativeA group of microorganisms which prefer or preferentially use molecular oxygen when available, but are capable of suing other pathways for energy and synthesis if molecular oxygen is not available.

Fahrenheit ScaleFahrenheit scale is the temperature scale in which 212 degrees is the boiling point of water and 32 degrees is the freezing point of water. The scale was invented in 1714 by a German physicist G.D. Fahrenheit (1686-1736).

32°F = 0°C212°F = 100°C1°F =(5/9)°CT(°C) = (5/9)[T(°F) - 32]T(°F) = (9/5)T(°C) + 32

FaradFarad (F) is the SI derived unit of electric capacitance. The farad is the capacitance of an electric capacitor between the two plates of which there appears a difference of electric potential of one volt when it is charged by a quantity of electricity equal to one coulomb (F = C/V). The unit is named after the British scientist M. Faraday (1791-1867).

ORAfter Michael Faraday, English (1791-1867). The farad is a unit of electrical capacitance.

Faraday ConstantFaraday constant (F) is the electric charge of 1 mol of singly charged positive ions.

F = NA × e = 96487 C mol-1

where NA is Avogadro's constant (6.022 × 1023 mol-1) and e is the elementary charge (1.602 × 10-19 C).

FatigueFailure, at relatively low stress levels, of structures that are subjected to fluctuating and cyclic stresses.

Fatty AcidsFatty acids are aliphatic monocarboxylic acids characterized by a terminal carboxyl group (R-COOH). Natural fatty acids commonly have a chain of 4 to 28 carbons (usually unbranched and even-numbered), which may be saturated or unsaturated. The most important of saturated fatty acids are butyric (C4), lauric (C12), palmitic (C16), and stearic (C18). The most common unsaturated acids are oleic, linoleic, and linolenic (all C18).The physical properties of fatty acids are determined by chain length, degree of unsaturation, and chain branching. Short-chain acids are pungent liquids, soluble in water. As chain length increases, melting points are raised and water-solubility decreases. Unsaturation and chain branching tend to lower melting points.

ORA naturally occuring, usually in fats, monobasic carboxylic acid, with a long hydrocarbon tail chains.

FeedstockA raw material that can be converted to one or more products.

Fermentation

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Energy production without the benefit of oxygen as a terminal electron acceptor, i.e. oxidation in which the net effect is one organic compound oxidizing another. See respiration.ORThe decomposition of organic material to alcohol, methane, etc., by organisms, such as yeast or bacteria, usually in the absence of oxygen.

Fermi EnergySee Fermi Level

Fermi LevelFermi level is the highest energy of occupied states in a solid at zero temperature. The Fermi level in conductors lies in the conduction band, in insulators it lies in the valence band, and in semiconductors it falls in the gap between the conduction band and the valence band. It is named after the Italian physicst Enrico Fermi (1901 - 1954).

ORFor a metal, the energy corresponding to the highest filled electron state in the valence bond at 0 K.

FermionFermion is any particle with spin equal to an odd multiple of 1/2. Fermion is a particle that obeys Fermi-Dirac statistics, e.g. electron, proton, neutron, muon, etc.

FerritesFerrites are ceramic materials of nominal formula MO.Fe2O3, where M is a divalent metal (Co, Mn, NI, or Zn). The ferrites show either ferrimagnetism or ferromagnetism, but are not electrical conductors, and they are used in high-frequency circuits as magnetic cores, in rectifiers on memory and record tapes, and various related uses in radio, television, radar, computers, and automatic control systems.

ORBody-centered cubic iron. Also, iron and steel alloys that have the BCC crystal structure.

FerroelectricA dielectric material that may exhibit polarization in the absence of an electric field.

FerromagnetismFerromagnetism is a type of magnetism in which the magnetic moments of atoms in a solid are aligned within domains which can in turn be aligned with each other by a weak magnetic field. The total magnetic moment of a sample of the substance is the vector sum of the magnetic moments of the component domains. In an unmagnetized piece of ferromagnetic material the magnetic moments of the domains themselves are not aligned; when an external field is applied those domains that are aligned with the field increase in size at the expense of the others. Ferromagnetic materials can retain their magnetization when the external field is removed, as long as the temperature is below a critical value, the Curie temperature. They are characterized by a large positive magnetic susceptibility.

ORPermanent and large magnetizations found in some metals (e.g., Fe, Ni, and Co), which result from the parallel alignments of neighboring magnetic moments.

ORMany substances are found to be magnetic, in that they are attracted by magnetic and electric fields, but it is found that the metals iron, cobalt, nickel and a number of alloys posses a greater level of magnetism than other substances. This powerful magnetism is called ferromagnetism, and is due to a large magnetic moment in the atoms of the metals due to an unbalanced spin of the electrons in their inner orbits.

Fertiliser

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Substance that adds inorganic or organic plant nutrients to soil and improves its ability to grow crops, trees, or other vegetation.

FiberAny material that has been drawn into a cylinder with a length-to-diameter ratio greater than about ten.

Fick’s LawFick's law is the statement that the flux J of a diffusing substance is proportional to the concentration gradient, i.e.,

J = -D(dc/dx)where D is called the diffusion coefficient.

FillerAn inert foreign substance added to a matrix to improve or modify its properties.

Fire PointFire point is the lowest temperature at which a liquid or volatile solid gives off vapour sufficient or forms higher vapour pressure to form an ignitable mixture with the air near the surface of the liquid or within the test vessel, and if a fire source brought near to that mixture, it will continue burning for at least 5 (five) seconds.

ORThe lowest temperature at which sufficient vapour is produced to cause combustion for at least five seconds, if an ignition source is present.

ORIt is the lowest temperature, at which, if an ignition source is brought near the substance, the substance will ignite (burn) for at least five seconds.

FiringA high-temperature heat treatment that increases the density and strength of a ceramic piece.

Fixed solidsThese are the solids that do not volatilize at 550°C.

Fixed suspended solidsIt is the matter remaining from the suspended solids analysis which will not burn at 550°C. It represents the non-filterable inorganic residue in a sample.

Flame retardantsAny chemical compound used to raise the ignition point of such materials as cloth or plastic, and thereby increase their resistance to combustion

FlammableA material which is easily ignited.

Flash PointFlash point is the lowest temperature at which a liquid or volatile solid gives off vapour sufficient or forms higher vapour pressure to form an ignitable mixture with the air near the surface of the liquid or within the test vessel (NFPA).

ORThe lowest temperature at which sufficient vapour is produced to cause combustion for a moment, if an ignition source is present.

OR

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It is the lowest temperature, at which, if an ignition source is brought near the substance, the substance will ignite (burn) for a moment, but does not continue burning.

ORThe minimum temperature at which sufficient vapour is released by a liquid or solid (fuel) to form a flammable vapour-air mixture at atmospheric pressure.

FlocculantFlocculants are products used in waste treatment to separate unwanted components from water and sludge.

Flocculant SettlingSettling in which particle concentrations are sufficiently high that particle agglomeration occurs. This results in a reduction in the number of particles and an increase in average particle mass. As agglomeration occurs higher settling velocities result.

Flue GasThe gas resulting from the combustion of a fuel that is emitted to the flue.

FluidizationThe suspension of particles by sufficient upward velocity of the fluid. During fluidization the gravity force is overcome by a combination of buoyancy and fluid friction.

FluorescenceThe slow emission of longer wavelength light following the absorption of shorter wavelength radiation. Fluorescence is common with aromatic compounds with several rings joined together. Phosphorescence is similar but may persist long after the stimulating radiation is extinguished.

FluxThe movement of a mass past a surface, plane, or boundary. The units are mass per unit area per unit time or [Kg/m2-hour].

FoamFoams are dispersions of gases in liquids or solids. The gas globule may be of any size, from colloidal to macroscopic, as in soap bubbles. Bakers' bread and sponge rubber are examples of solid foams. Typical liquid foams are those used in fire-fighting, shaving creams, etc. Foams made by mechanical incorporation of air are widely used in the food industry (e.g. whipped cream, egg white, ice cream, etc.). Foams can be stabilized by surfactants.

ForceAn entity that when applied to a mass causes it to accelerate. Sir Isaac Newton's Second Law of mation states: the magnitude of a force = mass * acceleration.

Forced ConvectionWhen the circulating currents are produced by an external agency such as an agitator in a reaction vessel, pump, fan or blower, the action is called forced convection. Here fluid motion is independent of density gradient.

ForgingMechanical forming of a metal or alloy by heating and hammering.

Fourier’s LawThe rate of heat flow at a given point in a body is proportional to the area of cross-section and the temperature gradient, at the given point.

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Q = -kA (dT/dn)Or q = Q/A = -k(dT/dn)where Q = Rate of heat flow

k = The proportionality constant (thermal conductivity)A = Area of cross-sectionT = Temperaturen = Distance measured normal to the surface (in the direction of heat flow)q = Heat Flux (i.e. Rate of heat flow per unit area)

Fractional DistillationA method for the separation of several volatile components of different boiling points, conducted by distilling the mixture at the lowest possible boiling point and collecting the distillate as one fraction until the temperature rises showing that a higher boiling component or mixture is beginning to distil. The receiver with fraction no. 1 s disconnected at this stage from the condenser and a new receiver substituted for it, which collects fraction no. 2, the next higher boiling fraction desired. When the temperature again rises, a third receiver substituted for it, which collects the next higher boiling fraction no. 3, and this method is continued until the highest boiling fraction has been distilled. For solutions, whose boiling point changes continuously with changes in composition, fractional distillation is also achieved in stages. The original solution is distilled until a certain fraction of the liquid has been vaporized, the distillate is then separately redistilled until a certain fraction of it is volatilized, and this process is kept up through several stages.

Fracture ToughnessCritical value of the stress intensity factor for which crack extensions occurs.

Free ConvectionWhen circulating currents arise from the heat transfer process itself, i.e. from density difference due to temperature difference/gradient in the fluid mass, it is called as free or natural convection.

Free ElectronElectron which is not attached to a nucleus.

Free EnergyThe energy of a system that is available to do work at constant temperature and pressure.

ORA thermodynamic quantity that is a function of both the internal energy and entropy of a system.

Free RadicalFree radical is a molecular fragment having one or more unpaired electrons, usually short-lived and highly reactive. They can be produced by photolysis or pyrolysis in which a bond is broken without forming ions. In formulas, a free radical is conventionally indicated by a dot (Cl∙). Free radicals are known to be formed by ionising radiation and thus play a part in deleterious degradation effects that occur in irradiated tissue. They also act as initiators or intermediates in oxidation, combustion, photolysis, and polymerisation.

ORFree radical is highly reactive molecule or atom with an unpaired electron. The species is often represented by a formula with a single dot as the unpaired electron (∙CH3, ∙SnH3, ∙Cl).

Frenkel DefectIn an ionic solid, a cation-vacancy and cation-interstitial pair.

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FreonA registered trademark for a cholorfluorocarbon (CFC) gas that is highly stable and that has been historically used as a refrigerant.

FrequencyFrequency (ν) is number of cycles of a periodic phenomenon divided by time. Hertz (Hz) is the SI derived unit, with a special name, for frequency, equal to s -1. It is named after the German scientist Heinrich Hertza (1857-1894).

ORNumber of events in a given unit of time. When describing a moving wave, means the number of peaks which would pass a stationary point in a given amount of time.

Friction HeadThe energy lost from the movement of a fluid in a conduit (pipe) due to the disturbances created by the contact of the moving fluid with the surfaces of the conduit, or the additional pressure that a pump must provide to overcome the resistance to fluid flow created by or in a conduit.

Froude NumberFroude number (Fr) is a dimensionless quantity used in fluid mechanics, defined by

Fr = υ / (l.g)1/2

where v is velocity, l is length, and g is acceleration due to gravity.

FSSee Fixed Solids

FSSSee Fixed Suspended Solids

Fuel OilIt is the liquid petroleum fraction, having higher molecular weight compounds known as asphaltic bitumens (having 17 – 30 carbon atoms). Fuel oils are essentially made up of residues remaining from atmospheric and vacuum distillation and conversion processes. On one extreme is the light fuel oil produced from cycle gas oil of cracking units and on the other extreme is the heavy fuel oils produced from residues of crude distillation units, thermal catalytic cracking units and coking units. Intermediate grade/viscosity of fuel oils are made by blending of distillates and residual stocks. Its boiling point ranges between 320 – 400°C. It is used for heating and power generation purpose, and may be cracked to provide gasoline. Light fuel oil may be used directly as a fuel for industrial furnaces, while heavy fuel oil is required to be blended with light fuel oil or naphtha to reduce its viscosity, and improve fluidity. It may also be cracked to produce gasoline, diesel, light fuel oil etc.

FugacityFugacity (f) is a thermodynamic function used in place of partial pressure in reactions involving real gases and mixtures. For a component of a mixture, it is defined by

dμ = RT(lnf)where μ is the chemical potential.

The fugacity of a gas is equal to the pressure if the gas is ideal. The fugacity of a liquid or solid is the fugacity of the vapour with which it is in equilibrium. The ratio of the fugacity to the fugacity in some standard state is the activity.

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GgThe force of acceleration due to gravity equal to 32.1739 ft/sec2 or 386 in./sec2.

Gage pressureAbsolute pressure minus local atmospheric pressure.

GalGal is a non-SI unit of acceleration, equal to 1 cm/s2. Also called galileo.

GallonGallon (US) is a unit of volume equal to 3.785412 L.Gallon (UK, Imperial) is a unit of volume equal to 4.546090 L.

Galvanized SteelA specially zinc-coated steel used on many major painted panels and in key unpainted areas of a vehicle to help prevent rust and corrosion.

Gamma RadiationGamma radiation is electromagnetic radiation of extremely short wavelength. Gamma radiation ranges in energy from about 10-15 to 10-10 J (10 keV to 10 MeV) (wavelength less than about 1 pm). Gamma rays are emitted by excited atomic nuclei during the process of passing to a lower excitation state.Gamma rays are extremely penetrating and are absorbed by dense materials like lead and uranium. Exposure to gamma radiation may be lethal.

ORThese are electromagnetic radiations beyond the X-rays in frequency. They are usually produced in nuclear reactions.

OROne of the three types of rays produced by radioactive disintegration, but gamma rays are the only one comprised of electromagnetic radiation. Gamma rays have a very short wavelength, and have the greatest penetrative power of all radioactive emissions.

ORA highly penetrating type of nuclear radiation, similar to x-rays and light, except that it comes from within the nucleus of an atom, and, in general, has a shorter wavelength. Gamma rays emission is a decay mode by which excited state of a nucleus de-excite to lower (more stable) state in the same nucleus.

Gamma RaysSee Gamma Radiations

GasGas is a state of matter in which the matter concerned occupies the whole of its container irrespective of its quantity.

Gas OilIt is a liquid petroleum distillate, usually includes diesel fuel, heating oils and light fuel oils. It has boiling point range between 250 - 320°C and has the carbon number ranging from 10 – 18.

Gas strippingGas transfer of an undesirable gas from a water stream to the atmosphere. Gasification

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The process in which a solid fuel is converted into a gas; also known as pyrolitic distillation or pyrolysis. Production of a clean fuel gas makes a wide variety of power options available.

GasolinePetrol, also known as motor spirit or gasoline, is one of the most widely used petroleum products. It is obtained during distillation within a temperature range 40 – 120 °C and is composed of hydrocarbons ranging from C5 to C9. The main types are:

a) Normal or Straight chain Paraffinsb) Iso or Branched chain Paraffinsc) Cycloparaffinsd) Aromatics

And e) OlefinsIt is highly volatile, inflammable and used as a fuel for internal combustion engines of

automobiles and aeroplanes and for dry cleaning of clothes.OR

A refined petroleum product suitable for use as a fuel in internal combustion engines.

GaussGauss (G) is a non-SI unit of magnetic flux density (B). 1 G = 10-4 T.

Gaussian System of UnitsGaussian system of units is a hybrid system used in electromagnetic theory, which combines features of both the electrostatic cgs subsystem (esu) and electromagnetic cgs subsystem (emu). With three base units, it uses em units in magnetism and es units in electrostatics. This involves using the constant c (the velocity of light in vacuum) to interrelate these sets of units.

Gay-Lussac’s LawSee Charles' law

Geiger CounterInstrument that measures radiation output.

ORA radiation detector consisting of two electrodes with a low-pressure gas in between. A voltage is maintains such that if radiation passing through the counter ionizes the gas, an avalanche of electrons will occur. Geiger counters can count radiation but cannot distinguish either the energy or kind of radiation.

GelGels are colloids in which both dispersed and continuous phases have a three-dimensional network throughout the material, so that it forms a jelly-like mass (e.g. gelatine). One component may sometimes be removed to leave a rigid gel (e.g. heating silica gel).

Gibbs Free EnergyGibbs free energy (G) is an important function in chemical thermodynamics, defined by

G = H-TSwhere H is the enthalpy, S the entropy, and T the thermodynamic temperature. Gibbs free energy is the energy liberated or absorbed in a reversible process at constant pressure and constant temperature. Sometimes called Gibbs energy and, in older literature, simply "free energy".

Changes in Gibbs free energy, ΔG, are useful in indicating the conditions under which a chemical reaction will occur. If ΔG is negative the reaction will proceed spontaneously to equilibrium. In equilibrium position ΔG = 0.

Gibbs Phase Rule

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Gibbs phase rule is the relationship used to determine the number of state variables, usually chosen from among temperature, pressure, and species composition in each phase, which must be specified to fix the thermodynamic state of a system in equilibrium:

F = C - P + 2where C is the number of components in a mixture, P is the number of phases, and F is the degrees of freedom, i.e., the number of intensive variables that can be changed independently without affecting the number of phases.

GlassAn inorganic product of fusion which has cooled to a rigid condition without crystallizing.

Glass-CeramicA fine-grained crystalline material that was formed as a glass and subsequently devitrified (crystallized).

Glass Transition TemperatureGlass transition temperature is the temperature at which an amorphous polymer is transformed, in a reversible way, from a viscous or rubbery condition to a hard and relatively brittle one.

Glauber’s SaltGlauber's salt is sodium sulfate decahydrate (Na2SO4×10H2O). Loses water of hydration at 100 °C. Energy storage capacity is more than seven times that of water.

Global WarmingThe long-term warming of the plant due to increases in greenhouse gases which trap reflected light preventing it from exiting to space.

GlyceridesGlycerides are esters of glycerol (propane-1,2,3-triol) with fatty acids, widely distributed in nature. They are by long-established custom subdivided into triglycerides, 1,2- or 1,3-diglycerides, and 1- or 2- monoglycerides, according to the number and positions of acyl groups.

GlycolsGlycols are compounds that have two hydroxyl groups present in each molecule. The simplest member is ethylene glycol - see below:

Graham’s LawThe rate of diffusion of a gas is inversely proportional to the square root of its molecular weight.

GrainGrain (gr) is a non-SI unit of mass, equal to 64.79891 mg.

Gram Equivalent WeightThe atomic weight of an element expressed in grams and divided by its valance. It is the weight, that corresponds chemically to or is equivalent to 1.0 gram, of hydrogen in acid or base reaction.

Gram MoleIt is defined as the mass in grams of a substance that is numerically equal to its molecular weight.

Grashof Number

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Grashof number (Gr) is a dimensionless quantity used in fluid mechanics, defined byGr = βgαΔTρ2/ η2

where T is temperature, ρ is density, l is length, η is viscosity, α is cubic expansion coefficient, and g is acceleration of gravity.

GravimetryGravimetry is the quantitative measurement of an analyte by weighing a pure, solid form of the analyte. Since gravimetric analysis is an absolute measurement, it is the principal method for analyzing and preparing primary standards. A typical experimental procedure to determine an unknown concentration of an analyte in solution is as follows:

- quantitatively precipitate the analyte from solution - collect the precipitate by filtering and wash it to remove impurities - dry the solid in an oven to remove solvent - weigh the solid on an analytical balance - calculate the analyte concentration in the original solution based on the weight of the precipitate.

Gravitational ConstantGravitational constant (G) is the universal constant in the equation for the gravitational force between two particles

F = Gm1m2/r2

where r is the distance between the particles and m1 and m2 are their masses.

GrayGray (Gy) is the SI derived unit of absorbed dose of radiation. The gray is the absorbed dose when the energy per unit mass imparted to matter by ionizing radiation is one joule per kilogram (Gy = J/kg). The unit is named after the British scientist Louis Harold Gray (1905-1965).

GreaseA mixture comprised of petroleum derived oil thickened until becomes a semisolid, by means of soaps of heavy metals such as calcium, aluminium, lead, etc. The high viscosity of greases enables them to withstand the severe mechanical action of machine parts, gears, and bearings even at temperature upto 700°C. It is used for lubricating purpose.

Greenhouse GasesGases which trap solar radiation. Of the solar energy entering the earth's atmosphere a portion is reflected back and a portion penetrates onto the earth's surface. The portion reflected back from the earth's surface is at a different wavelength that when it entered. Carbon dioxide and other gases, which pass solar radiation, absorb this reflected radiation, increasing the earth's temperature. This is much like a greenhouse, hence the name.

Grignard ReagentsGrignard reagents are organomagnesium halides, RMgX, having a carbon- magnesium bond (or their equilibrium mixtures in solution with R2Mg + MgX2).

Ground StateA lowest energy state of the nucleus.

GroundwaterWater which is contained in geologic strata. Also properly written as two words, ground water.

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HHalf-LifeFor a given reaction the half life t1/2 of a reactant is the time required for its concentration to reach a value that is the arithmetic mean of its initial and final (equilibrium) value.In nuclear chemistry, (radioactive) half life is defined, for a simple radioactive decay process, as the time required for the activity to decrease to half its value by that process.

N = N0/2OR

The amount of time it takes for half an initial amount to disintegrate.

Hall EffectThe phenomenon whereby a force is brought to bear on a moving electron or hole by a magnetic field that is applied perpendicular to the direction of motion. The force direction is perpendicular to both the magnetic field and the particle motion directions.

HalocarbonHalocarbon is a compound containing no elements other than carbon, one or more halogens, and sometimes hydrogen. The simplest are compounds such as tetrachloromethane (CCl4), tetrabromomethane (CBr4), etc. The lower members of the various homologous series are used as refrigerants, propellant gases, fireextinguishing agents, and blowing agents for urethane foams. When polymerized, they yield plastics characterized by extreme chemical resistance, high electrical resistivity, and good heat resistance.

HalogensThe halogens are the elements fluorine (F) chlorine (Cl), bromine (Br), iodine (I), and astatine (At). They are non-metals, and make up part of the 17 group in the periodic table. Compounds of these elements are called halogenides or halides.

The halogens all have a strong unpleasant odor and will burn flesh. They do not dissolve well in water. The five elements are strongly electronegative. They are oxidizing agents, with fluorine being the strongest and astatine being the weakest. They react with most metals and many non-metals.

Halogens form molecules which consists of atoms covalently bonded. With increasing atomic weight there is a gradation in physical properties. For example: Fluorine is a pale green gas of low density. Chlorine is a greenish-yellow gas 1.892 times as dense as fluorine. Bromine is a deep reddish-brown liquid which is three times as dense as water. Iodine is a grayish-black crystalline solid with a metallic appearance. And astatine is a solid with properties which indicate that it is somewhat metallic in character.

ORThis important group of elements occupies Group VII of the periodic table. Its first element, fluorine, is the most strongly electronegative element known. All halogens are electron defficient and readily share electrons with other elements to staisfy their valency needs, eg. they all form compounds with hydrogen, with the formula HX (where X=halogen)

HAPsHazardous air pollutants.

HardenabilityA measure of the depth to which a specific ferrous alloy may be hardened by the formation of martensite upon quenching from a temperature above the upper critical temperature.

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HardnessHardness is the resistance of a material to deformation of an indenter of specific size and shape under known load. This definition applies to all types of hardness scales except Mohs scale, which is a based on the concept of scratch hardness and is used chiefly for minerals. The most generally used hardness scales are Brinell (for cast iron), Rockwell (for sheet metal and heat-treated steel), Knoop (for metals).

ORThe sum of the divalent cation concentrations expressed as meq/L or mg calcium carbonate per liter [mg CaCO3/L]. It is important because hard waters require increased amounts of soap for bathing or washing clothes and because of scale formation on piping, cooking vessels, water heaters, boilers, heat exchangers, etc.

ORThe measure of some materials' resistance to deformation by surface indentation or by abrasion.

HCPSee Hexagonal Close Packed

HeadA unit of pressure for a fluid, commonly used in water pumping and hydro power to express height a pump must lift water, or the distance water falls. Total head accounts for friction head losses, etc.

Head LossThe loss of pressure in a flow system measured using a length parameter (i.e., inches of water, inches of mercury).

Head PressureExpression of pressure in terms of the height of fluid, P = yrg, where r is fluid density and y = the fluid column height. g = the acceleration of gravity.

HeatHeat is a form of energy associated with and proportional to molecular motion. It can be transferred from one body to another by radiation, conduction, or convection.

ORThermal energy. Heat is expressed in units of calories or BTU's.

Heat BalanceEnergy output from a system that equals energy input.

Heat CapacityHeat capacity is defined in general as dQ/dT, where dQ is the amount of heat that must be added to a system to increase its temperature by a small amount dT. The heat capacity at constant pressure is Cp = (∂H/∂T)p; that at constant volume is CV = (∂E/∂T)V, where H is enthalpy, E is internal energy, p is pressure, V is volume, and T is temperature. An upper case C normally indicates the molar heat capacity, while a lower case c is used for the specific (per unit mass) heat capacity.

Heat EngineA device that produces mechanical energy directly from two heat reservoirs of different temperatures. A machine that converts thermal energy to mechanical energy, such as a steam engine or turbine.

Heat FluxRate of Heat Transfer per unit area is known as Heat flux. It is denoted by letter ‘q’, and is given by:

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q = Q/A = -k(dT/dn)

whereQ = Rate of Heat Flowk = The proportionality constant (thermal conductivity)A = Area of cross-sectionT = Temperaturen = Distance measured normal to the surface (in the direction of heat flow)q = Heat Flux (i.e. Rate of heat flow per unit area)

Heat of atomizationIt is the energy required to dissociate one mole of a given substance into atoms.

Heat of combustion is the heat evolved when a definite quantity of a substance is completely oxidized (burned).

Heat of crystallization is the heat evolved or absorbed when one mole of given substance crystallizes from a saturated solution of the same substance.

Heat of formation is the heat evolved or absorbed when one mole of a compound is formed in their standard state from its constituent elements.

Heat of fusion is the heat required to convert a substance from the solid to the liquid state with no temperature change (also called latent heat of fusion or melting).Heat of hydration is the heat evolved or absorbed when a hydrate of a compound is formed.

Heat of reaction is the heat evolved or absorbed as a result of the complete chemical reaction of molar amounts of the reactants.

Heat of sublimation is the energy required to convert one mole of a substance from the solid to the gas state (sublimation) without the appearance of the liquid state.

Heat of vaporization is the heat required to convert a substance from the liquid to the gaseous state with no temperature change (also called latent heat of vaporization).

Heat PumpAn electricity powered device that extracts available heat from one area (the heat source) and transfers it to another (the heat sink) to either heat or cool an interior space or to extract heat energy from a fluid.

Heat Sink1. Thermodynamic - A body which can absorb thermal energy.2. Practical - A finned piece of metal used to dissipate the heat of solid state components mounted on it.

Heat TransferThe process of thermal energy flowing from a body of high energy to a body of low energy. Means of transfer are: conduction; the two bodies contact. Convection; a form of conduction where the two bodies in contact are of different phases, i.e. solid and gas. Radiation: all bodies emit infrared radiation.

ORThe flow of heat from one area to another by conduction, convection, and/or radiation. Heat flows naturally from a warmer to a cooler material or space.

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Heat TreatingA process for treating metals where heating to a specific temperature and cooling at a specific rate changes the properties of the metal.

Heating ValueSee Calorific Value

Heavy WaterA molecule of water contains two atoms of hydrogen and one of oxygen. Most water comprises of hydrogen/oxygen but a small percentage is composed of another hydrogen isotope, deuterium and oxygen. Deuterium differs from hydrogen by having one neutron in the nucleus of each atom. Deuterium water is given the formula D2O. There is approx. 1 part in 5000 D2O in normal water and it can be concentrated by electrolysis. D2O had a higher boiling point (101.4 °C) and melts at 3.6 °C

HectareHectare (ha) is a unit of area equal to 104 m2. The unit is still used in agriculture.

Heisenberg Uncertainty PrincipleHeisenberg uncertainty principle is the principle that it is not possible to know with unlimited accuracy both the position and momentum of a particle. German physicist Werner Heisenberg (1901-1976) discovers this principle in 1927.

ORThis principle states that it is not possible to know a particle's location and momentum precisely at any time.

Helmholz Free EnergyHelmholz free energy (A) is a thermodynamic function defined by A = U - TS, where U is the internal energy, S the entropy, and T the thermodynamic temperature. For a reversible isothermal process ΔA represents the useful work available.

HenryHenry (H) is the SI derived unit of inductance equal to the inductance of a closed circuit in which an e.m.f. of one volt is produced when the electric current in the circuit varies uniformly at the rate of one ampere per second (H = V∙s/A). The unit is named after the US physicst Joseph Henry (1797-1878).

ORAfter Joseph Henry, U.S. (1797-1878). The henry is a unit of electrical inductance.

Henry’s LawHenry's law is discovered in 1801 by the British chemist William Henry (1775-1836). At a constant temperature the concentration of gas dissolved in a liquid at equilibrium is proportional to the partial pressure of the gas. It applies only to gases that not react with the solvent.

pA = H.xA

where pA is the partial pressure of component above the solution, xA is its mole fraction in the solution, and Kx is the Henry's law constant (a characteristic of the given gas and solvent, as well as the temperature).

HertzHertz (Hz) is the SI derived unit, with a special name, for frequency. The hertz is the frequency of a periodic phenomenon of which the period is one second (Hz = 1 s-1). It is named after the German scientist Heinrich Hertza (1857 - 1894).

OR

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After Heinrich Rudolf Hertz, German (1857-1894). The hertz is a unit of frequency: 1 hertz = 1 cycle per second. Thus, 1 kilocycle and 1 kilohertz both equal 1,000 cycles per second.

ORUnits in which frequency is expressed. Synonymous with cycles per second.

Heterocyclic CompoundHeterocyclic compounds are cyclic compounds having as ring members atoms of at least two different elements, e.g., quinoline, 1,2-thiazole.

Heterocyclic MoleculeA molecule containing at least one ring of carbon atoms, and which also has at least one atom from a different element, (nitrogen, sulphur, oxygen etc..) within the ring. Examples are shown below:HeterogeneousIn which, materials are not uniform throughout.

ORContaining more than one phase.

HeterotrophicA group of organisms which obtain carbon for synthesis from other organic matter or proteins.

Heusler AlloysHeusler alloys are alloys of manganese, copper, aluminum, nickel, and sometimes other metals which find important uses as permanent magnets.

Hexagonal Close PackedA crystal structure found for some metals. The HCP unit cell is of hexagonal geometry and is generated by the stacking of close-packed planes of atoms.

High-Performance Liquid ChromatographySee HPLC

High Speed Diesel OilHigh Speed Diesel Oil also known as HSD is widely used in diesel engines for automotive purposes, as in buses, trucks, and other diesel locomotives.

Hindered SettlingSettling in which particle concentrations are sufficient that particles interfere with the settling of other particles. Particles settle together as a body or structure with the water required to traverse the particle interstices.

Hole (Electron)For semi-conductors and insulators, a vacant electron state in the valence band that behaves as a positive charge carrier in an electric field.

HolographyHolography is a technique for creating a three-dimensional image of an object by recording the interference pattern between a light beam diffracted from the object and a reference beam. The image can be reconstructed from this pattern by a suitable optical system.

HomogeneousIn which, materials are the same throughout. All solutions are homogeneous.

OR

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Containing a single phase.

HomopolymerA polymer having a chain structure in which all mer units are of the same type.

Hooke’s LawWhen a load is applied to any elastic body is deformed or strained, then the resulting stress (the tendency of the body to resume its normal condition) is proportional to the strain. Stress is measured in units of force per unit area, strain is the extent of the deformation.

ORDefines the basis for the measurement of mechanical stresses via the strain measurement. The gradient of Hooke's line is defined by the ratio of which is equivalent to the Modulus of Elasticity E (Young's Modulus).

Horse PowerHorse power is obsolete non-SI of power introduced by James Watt in 1782 to allow to describe the power of steam machinery. It was equal to the work effort of a horse needed to raise vertically 528 cubic feet of water to one metre in one minute (HP = 735.498750 W).

Hot WorkingAny metal forming operation that is performed above a metal recrystallization temperature.

HPLCHPLC is abbreviation for high-performance liquid chromatography. HPLC is a variation of liquid chromatography that utilizes high-pressure pumps to increase the efficiency of the separation.

HSDSee High Speed Diesel Oil

HumidifierA device used to maintain a specified humidity in a conditioned space.

HumidityA measure of the moisture content of air; may be expressed as absolute, mixing ratio, saturation deficit, relative, or specific.

HydrationHydration is addition of water or the elements of water (i.e. H and OH) to a molecular entity. The term is also used in a more restricted sense for the process:

A+B- ⇌ A+(aq) + B-(aq)

Hydraulic Set CementA cement that sets through reaction with water.

HydrocarbonHydrocarbon is a compound containing only carbon and hydrogen.

ORAny organic compound composed entirely of carbon and hydrogen. Two examples are methane gas and octane.

ORA molecule comprised solely of carbon and hydrogen. The simplest example is Methane.

Hydrodealkylation

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The term is used to describe a method of removing alkyl groups from a hydrocarbon compound and replacing them with hydrogen. This is done by treating the compound with hydrogen at high temperature and pressure.

Hydrogen Bondis a special situation that exists between the hydrogen atom in one molecule (like water) and the oxygen atom in another molecule (like another water molecule). This bond is ten times weaker than the covalent bond, and ten times stronger than the van der waals force. The hydrogen bond caused water to have its unusual properties of high boiling point, high melting point, high surface tension, and its formation of the six- sided ring structure in ice. The latter causes water to expand upon freezing, become less dense, and float in water.

ORStrong type of intermolecular dipole-dipole atttraction. Occurs between hydrogen and F, O or N.

ORA strong secondary interatomic bond which exists between a bound hydrogen atom (its unscreened proton) and the electrons of adjacent atoms.

ORA bond formed by a hydrogen atom to an electronegative atom, and is denoted X---H-B.

Hydrogen IonThe ion which is left when the hydrogen atom loses its electron, forming a proton. In water the hydrogen ion binds to the water molecules, producing H3O+. Compound which exhibit hydrogen bonding include water and amines.

Hydrogen Ion Activity (aH+)Activity of the hydrogen ion in solution. Related to hydrogen ion concentration (CH+) by the activity coefficient for hydrogen (f H+).

HydrogenationIt is the process of catalytic addition of hydrogen molecule to organic compound molecule containing multiple bond. Reactions of hydrogen with inorganic materials are not considered as hydrogenation.

HydrolysisHydrolysis is a chemical reaction in which water reacts with another substance to form two or more new substances. This involves ionization of the water molecule as well as splitting of the compound hydrolyzed, e.g.

CH3COOC2H5 + H2O ⇌ CH3COOH + C2H5OHExamples are conversion of starch to glucose by water in presence of suitable catalysts and reaction of the ions of a dissolved salt to form various products, such as acids, complex ions, etc.

ORWhen water reacts with another substance and as a result the oxygen in water makes a bond with the substance.

HydrophilicHydrophilic is having a strong tendency to bind or absorb water, which results in swelling and formation of reversible gels. This property is characteristic of carbohydrate.HydrophobicHydrophobic is antagonistic to water, incapable of dissolving in vater. This property is characteristic of oill, fats, waxes, and many resins.

Hydrophobic Interaction

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Hydrophobic interaction is the tendency of hydrocarbons (or of lipophilic hydrocarbon-like groups in solutes) to form intermolecular aggregates in an aqueous medium, and analogous intramolecular interactions. The name arises from the attribution of the phenomenon to the apparent repulsion between water and hydrocarbons. Use of the misleading alternative term hydrophobic bond is discouraged.

HygroscopicCapacity to absorb water.

Hypereutectoid AlloyFor an alloy system displaying a eutectoid, an alloy for which the concentration of solute is greater than the eutectoid composition.

Hypoeutectoid AlloyFor an alloy system displaying a eutectoid, an alloy for which the concentration of solute is less than the eutectoid composition

HypolimnionThe lower layer of a lake.

Hysteresis (Magnetic)The irreversible magnetic flux density-versus-magnetic field strength (B-versus-H) behavior found for ferromagnetic and ferrimagnetic materials.

ORThe difference in output when the measurand value is first approached with increasing and then with decreasing values. Expressed in percent of full scale during any one calibration cycle. See also Deadband.

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IIdeal GasIdeal gas is a gas in which there is complete absence of cohesive forces between the component molecules; the behavior of such a gas can be predicted accurately by the ideal gas equation through all ranges of temperature and pressure. The concept is theoretical, since no actual gas meets the ideal requirement.

Ideal Gas LawThe generalized ideal gas law is derived from a combination of the laws of Boyle and Charles. Ideal gas law is the equation of state

pV = nRTwhich defines an ideal gas, where p is pressure (kPa), V molar volume (m3), T temperature (K), n is number of moles (kmol), and R the molar gas constant [8.31451 m3.kPA/(kmol.K)]

ORpV=nRT

Describes the relationship between pressure (p), temperature (T), volume (V), and moles of gas (n). It is not completely accurate, and becomes less accurate as conditions become less ideal.

Ideal SolutionIdeal solution is a solution in which solvent-solvent and solvent-solute interactions are identical, so that properties such as volume and enthalpy are exactly additive. Ideal solutions follow Raoult's law, which states that the vapour pressure pi of component i is pi = xi pi

*, where xi is the mole fraction of component i and pi

* the vapour pressure of the pure substance i.

IdentityA math property which states: A+0=A and A*1=A.

Ignition PointThe minimum temperature at which combustion of a solid or fluid can occur.

ImmiscibleTwo liquids are said to be immiscible, if when added together they do not mix but form two separate liquid phases.

Impact EnergyA measure of the energy absorbed during the fracture of a specimen of standard dimensions and geometry when subjected to very rapid (impact) loading. Charpy and Izod impact tests are used to measure this parameter, which is important in assessing the ductile-to-brittle transition behavior of a material.

ImpurityA substance unintentionally contained in a product other than the desired substance.

In Situ TreatmentTreatment of a waste in place, as opposed to pumping or digging the waste up and then treating it.

Index of RefractionSee Refractive Index

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IndicatorIndicator is a substance used to show the presence of a chemical substance or ion by its colour. Acid-base indicators are compounds, such as phenolphtaleine and methyl orange, that change colour reversibly, depending on whether the solution is acidic or basic. Oxidation-reduction indicators are substances that show a reversible colour change between oxidized and reduced forms.

ORA number of complex organic molecules can change their molecular structure and colour when faced with different pH conditions. The most well known indicator is litmus, which is a mixture of vegetable dyes. A list of common synthetic dyes is given below:

Infectious DiseaseA disease caused by pathogenic organisms.

InfiltrationThe movement of water from the surface of the land through the unsaturated zone and into the groundwater. This occurs during and immediately after precipitation events. It can also occur at the bottom of lakes and rivers.

InfluentThe fluid entering a system, process, tank, etc. An effluent from one process can be an influent to another process. See effluent.

Infrared RadiationsElectromagnetic radiation whose wavelength is longer than that of visible light, and is responsible for the transmission of radiant heat.

InhibitorA substance which is added to another substance to prevent an unwanted chemical reaction from occurring.

Inorganic ChemicalsA category of chemicals that do not include carbon and its derivatives as principal elements.

InsulatorInsulator is a material in which the highest occupied energy band (valence band) is completely filled with electrons, while the next higher band (conduction band) is empty. Solids with an energy gap of 5 eV or more are generally considered as insulators at room temperature. Their conductivity is less than 10-6 S/m and increases with temperature.

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Intensity BranchingThe intensity of a radiation emitted during radioactive decay.

IntermetallicA compound of two metals that has a distinct chemical formula. The bonds in intermetallic compounds are often partly ionic.

Intermolecular ForcesForces between molecules.

International System of UnitsSee SI Units

International Union of Pure and Applied Chemistry International Union of Pure and Applied Chemistry (IUPAC) is a voluntary nonprofit association of national organizations representing chemist in 45 member countries. It was formed in 1919 with the object of facilitating international agreement and uniform practice in both academic and industrial aspects of chemistry.

Intramolecular ForcesForces within molecules. Forces caused by the attraction and repulsion of charged particles.

Intrinsic SemiconductorA semiconductor material for which the electrical behavior is characteristic of the pure material.

Invariant PointA point on a binary phase diagram at which three phases are in equilibrium.

InverseA math property which states: A+(-A)=0 and A*(1/A)=1

IonIon is an atomic or molecular particle having a net electric charge.

ORIt is a charged atom or group of atoms. Ionization is caused by a gain or loss of electrons. A loss leaves a positive charge, a gain leaves a negative charge.

ORRemoving or adding electrons to an atom creates an ion (a charged object very similar to an atom).

ORAn electrically charged atom or group of atoms. If an atom or molecule gains an electron - it becomes a negatively charged anion, or if it loses an electron it becomes a positively charged cation.

Ion Dipole ForcesIntermolecular force that exist between charged particles and partially charged molecules.

Ion ExchangeIon exchange is a process involving the adsorption of one or several ionic species accompanied by the simultaneous desorption (displacement) of one or more other ionic species.

ORAn adsorption process in which one ion is exchanged for another ion of like charge. There is an equivalence of exchanged charge.

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Ion ExchangerIon-exchanger is a solid or liquid material containing ions that are exchangeable with other ions with a like charge that are present in a solution in which the material is insoluble. Ion-exchange resins consist of various copolymers having a cross-linked three-dimensional structure to which ionic groups have been attached.

Ion-NegetiveThese are those which have gained electrons and therefore have more negative charges than positive charges (protons).

Ion-PositiveThese are those which have lost electrons and therefore have fewer negative charges than positive charges (protons).

Ionic BondWhen two oppositely charged atoms share at least one pair of electrons but the electrons spend more time near one of the atoms than the other.

Ionic StrengthIonic strength (μ or I) is a measure of the total concentration of ions in a solution, defined by

μ = [Σcizi]/2where zi is the charge of ionic species i and ci is its concentration.

Ionization EnergyIonization energy is the minimum energy required to remove an electron from an isolated atom or molecule (in its vibrational ground state) in the gaseous phase.

ORIt is the minimum energy needed to remove an electron from an atom.

OREnergy required to remove an electron from a specific atom.

Ionization Energy - FirstIt takes off the first (outermost) electron.

Ionization Energy - SunsequentThese remove more electrons. The factors that determine the ionization energies are: distance from the nucleus (inverse square law) whether the orbital is filled or half-filled whether there is a noble gas structure the shielding effect of electrons in lower orbitals the ratio of protons to remaining electrons (guards to prisoners ratio) IonizesWhen a substance breaks into its ionic components.

Irreversible reactionA reaction in which the reactant(s) proceed to product(s), but the products react at an appreciable rate to reform reactant(s).

IsobarIsobar is a line connecting points of equal pressure on a graphical representation of a physical system.

IsobarsIsobars are nuclide having the same mass number but different atomic numbers. 54Cr and 54Fe, 112Cd and 112Sn are isobars.

OR

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Nuclides of the same atomic mass but different atomic number.

IsochoreIsochore is a line or surface of constant volume on a graphical representation of a physical system.

Isoelectric PointIsoelectric point is the pH of a solution or dispersion at which the net charge on the macromolecules or colloidal particles is zero. In electrophoresis there is no motion of the particles in an electric field at the isoelectric point.

IsomerisationThe chemical process by which a compound is transformed into any of its isomers i.e., forms with the same chemical composition but with different structure or configuration and, generally different physical and chemical properties

ORIt is the method used to convert straight chain hydrocarbons (n-paraffins) to branched chain hydrocarbons (iso-paraffins) in the presence of a catalyst. The main purpose of isomerization operation is to obtain higher octane number hydrocarbon from a hydrocarbon having lower octane number. Commercially, it is mostly practiced to obtain iso0butane from n-butane, which is then used in the production of good quality gasoline by alkylation. There are two processes for isomerization namely :

1) Low Temperature IsomerizationAnd 2) High Temperature Isomerization

IsomerismIf a molecule possesses the same molecular formula, but the atoms are arranged in a different way, then they are called isomers. Isomers have different physical and chemical properties from each other. Optically active isomers differ only in the fact one is the mirror image of the other, as shown with lactic acid below:

Many isomers occur as a result of different substituents occupying different positions on a benzene ring - see below:

IsomersIsomers are compounds that have identical molecular formulae but differ in the nature or sequence of bonding of their atoms (structural isomerism) or in the arrangement of their atoms in space (stereoisomerism).

OR

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Two or more different compounds with the same chemical formula but different structure and characteristics.

ORA long-lived excited state of the nucleus. Arbitrarily defined in as the Table of Isotopes as having a half-life greater than 1 ms.

IsomorphismIsomorphism is the existence of two or more substances that have the same crystal structure, so that they form solid solutions.

IsotacticA type of polymer chain configuration wherein all side groups are positioned on the same side of the chain molecule.

ORMeans geometrically regular. A polymer is isotactic if all of the groups attched to the back bone are arranged in the same geometrical pattern. See atactic.

IsothermIsotherm is a line connecting points of equal temperature on a graphical representation of a physical system.

Isothermal ProcessIsothermal process is a thermodynamic process in which the temperature of the system does not change.

IsotonesIsotones are nuclides having the same neutron number N but different atomic number Z.

IsotopesIsotopes are two or more nuclides with the same atomic number Z but different mass number A. The term is sometimes used synonymously with nuclide, but it is preferable to reserve the word nuclide for a species of specific Z and A.

ORThese are the same elements with different mass numbers. This is caused by having a different number of neutrons in the nucleus.

ORElements with the same number of protons but have different numbers of neutrons, and thus different masses.

ORAtoms of the same element having the different masses.

ORAll atoms of the same element posses the same no. of protons and electrons but not neccarily the same no. of neutrons. So all atoms of an element will react in the same way, but they can differ in their molecular masses. Atoms of the same element with different masses are known as isotopes. Hydrogen has three isotopes. 99.98% of all hydrogen has one proton and one electron, while 0.02% of hydrogen has one proton, one neutron and one electron. This isotope is called deuterium. There is also a trace of a third isotope, tritium, which has two neutrons in its nucleus.

ORTwo or more nuclides having the same atomic number, thus constituting the same element, but differing in the mass number. Isotopes of a given element have the same number of nuclear protons but differing numbers of neutrons. Naturally occurring chemical elements are usually mixtures of isotopes so that observed (non-integer) atomic weights are average values for the mixture.

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IsotropyIsotropy is the property of molecules and materials of having identical physical properties in all directions.

IUPACSee “International Union of Pure and Applied Chemistry”

Izod Impact TestOne of two tests that may be used to measure the impact energy of standard notched specimen.

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JJouleJoule (J) is the SI derived unit of energy, work, and heat. The joule is the work done when the point of application of a force of one newton is displaced a distance of one metre in the direction of the force (J = N m). The unit is named after the British scientist James Prescott Joule (1818-1889).

ORThe basic unit of thermal energy.

Joule-Thomson CoefficientJoule-Thomson coefficient (μ) is a parameter which describes the temperature change when a gas expands adiabatically through a nozzle from a high pressure to a low pressure region. It is defined by

μ = (∂T/∂p) H

where H is enthalpy.

Joule’s LawThe rate of heat production by a steady current in any part of an electrical circuit that is proportional to the resistance and to the square of the current, or, the internal energy of an ideal gas depends only on its temperature.

JunctionThe point in a thermocouple where the two dissimilar metals are joined.

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KKelvinKelvin (K) is the SI base unit of thermodynamic temperature. The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The unit is named after the British scientist Sir. W. Thompson, Lord Kelvin (1824-1907).

ORThe SI Unit of temperature. It is the degrees celsius plus 273.

ORAfter William Thomson Lord Kelvin, British (1824-1907). The kelvin is the unit of absolute temperature. Thus, absolute zero is zero kelvin, symbolized by 0 L. And water, which boils at 212 degrees F., or 100 degrees C., boils also at 373.15 K.

ORSymbol K. The unit of absolute or thermodynamic temperature scale based upon the Celsius scale with 100 units between the ice point and boiling point of water. 0°C = 273.15K (there is no degree (°) symbol used with the Kelvin scale).

KerogenA fossilized organic material present in oil shale and some other sedimentary rocks.

KeroseneKerosene oil is the distillate fraction of crude oil in the boiling range of 150 - 250°C. It never burns in the liquid state, but it has to in the form of vapor and mixed with the oxygen in the air in the correct ratio to form a combustible mixture. Various types of hydrocarbons present in kerosene are paraffins, naphthenes, aromatics and non-hydrocarbon compounds (sulfur, nitrogen, oxygen, and metals). Carbon number of the hydrocarbons present in kerosene ranges from 10 to 14. It is mainly used as a domestic fuel. It is also used as an illuminant, tractor fuel , in manufacture of insecticides, herbicides, fungicides and for preparing laboratory gases.

KetonesKetones are compounds in which a carbonyl group is bonded to two carbon atoms: R1R2C=O (neither R may be H). They are derived by oxidation of secondary alcohols. The simplest member of the series is acetone, (CH3)2CO.

OROrganic compounds with two hydrocarbon groups bonded to a carbonyl group.

ORAn organic compound containing the carbonyl group, >C=O, to which other carbon atoms are attached. Ketones are extremely useful as solvents and paint components. An example is Butanedione.

KilogramKilogram (kg) is the SI base unit of mass; it is equal to the mass of the international prototype of the kilogram.

The prototype of the standard is a cylinder of platinum-iridium alloy, 39 mm in diameter and 39 mm high. Prototype of the kilogram kept by the Bureau International des Poids et Mesures (International Bureau of Weights and Measures)

KilowattEquivalent to 1000 watts.

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Kilowatt Hour1000 watthours.

Kilovolt amperes (kva)1000 volt amps.

Kinematic ViscosityThe absolute viscosity of a fluid divided by its fluid density, i.e.

η = μ / ρ

Kinetic EnergyEnergy an object has because of its mass and velocity. Objects that don't move have no kinetic energy. (Kinetic Energy=0.5* mass*velocity2.

ORKinetic energy is energy of motion and is usually defined as the work that will be done by body possessing the energy when it is brought to rest. For a body of mass m having a speed v, the kinetic energy is mv2/2. Kinetic energy is most clearly exhibited in gases, in which molecules have much greater freedom of motion than in liquids and solids.

OREnergy associated with mass in motion, i.e., mV2/2 where m is the mass of the moving mass and V is its velocity.

Kirchhoff’s LawIt states that at thermal equilibrium ‘for all bodies’, the ratio of the emissive power to the absorptivity will be the same, i.e.:

E1/a1 = E2/a2 = E3/a3 = Eb/ab = Eb

(Since absorptivity of black body is 1)where E = Emissive Power & a = absorptivity

Kjeldhal FlaskKjeldhal flask is a round bottom flask with a long wide neck that is used in the determination of nitrogen by Kjeldhal's method.

Kjeldhal’s MethodKjeldhal's method is an analytical method for determination of nitrogen in certain organic compounds. The method was developed by the Danish chemist Johan Kjeldahl (1849-1900).It involves addition of a small amount of anhydrous potassium sulfate to the test compound, followed by heating mixture with concentrated sulfuric acid, often with a catalyst such as copper sulfate. As a result ammonia is formed. After alkalyzing the mixture with sodium hydroxyde, the ammonia is separated by distilation, collected in standard acid, and the nitrogen determined by back-titration.

KnockingUndesired ignition of a portion of a motor fuel in the cylinder head due to spontaneous oxidation reactions rather than to spark. This is not only noisy but also causes loss of power, particularly in high-compression systems. It can be reduced by the presence of branched chain hydrocarbons in the fuel and virtually eliminated by anti-knock agents such as tetraethyl-lead and manganese tricarbonyl. The use of these is declining because of their toxicity, their reputed contribution to air pollution, and their adverse effect on catalytic exhaust gas converters. In their place, increasing use is being made of non-metallic antiknock agents, such as methyl tert-butyl ether (MTBE) or a mixture of methanol and tert-butyl alcohol.

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Knudsen NumberKnudsen number (Kn) is a dimensionless quantity used in fluid mechanics, defined by

Kn = λ/lwhere λ is mean free path and l is length.

Kohlrausch’s LawIf a salt is dissolved in water, the conductivity of the solution is the sum of the conductances of the anions and cations. The law, which depends on the independent migration of ions, was deduced experimentally by German chemist Friedrich Kohlrausch (1840-1910).

KWSee Kilowatt

KWHSee Kilowatt Hour

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LLaminar FlowLaminar flow is smooth, uniform, non-turbulent flow of a gas or liquid in parallel layers, with little mixing between layers. It is characterized by small values of the Reynolds number.

ORStreamlined flow of a fluid where viscous forces are more significant than inertial forces, generally below a Reynolds number of 2000.

LandfillA legal and controlled area for the placement of wastes into the ground. See dump.

LandfillingThe placement of wastes into the land under controlled conditions to minimize their migration or effect on the surrounding environment.

LanthanidesLanthanides (lanthanons, lanthanoids or rare-earth elements) are a series of fourteen elements in the periodic table, generally considered to range in proton number from cerium to lutetium inclusive. It was convenient to divide these elements into the cerium group or light earth: cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu); and the yttrium group or heavy earths: gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) i lutetium (Lu). The position of lanthanum is somewhat equivocal and, although not itself a lanthanides, it is often included with them for comparative purpose. The lanthanides are sometimes simply called the rare earths. Apart from unstable Pm the lanthanides are actually not rare. Cerium is the 26. most abundant of all elements, 5 times as abundant as Pb. All are silvery very reactive metals.

ORThis is a group of fifteen closely related elements and are known as the rare earth or "inner transition" elements. They are so alike that they are difficult to seperate from each other and usually all occur together in nature.

LaserLaser (light amplification by stimulated emission of radiation) is a light amplifier usually used to produce monochromatic coherent radiation in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum.

ORAn acronym for light amplification by stimulated emission of radiation.

Latent HeatLatent Heat (L) is the quantity of heat absorbed or released when a substance changes its physical phase at constant temperature (e.g. from solid to liquid at the melting point or from liquid to gas at the boiling point).

ORExpressed in BTU per pound. The amount of heat needed (absorbed) to convert a pound of boiling water to a pound of steam.

ORThe change in heat content that occurs with a change in phase and without change in temperature.

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LatexA water emulsion of a synthetic rubber or plastic obtained by polymerization and used especially in coatings, paints and adhesives.

LatticeThe regular geometrical arrangement of points in crystal space.

Lattice ConstantsLattice constants are parameters specifying the dimensions of a unit cell in a crystal lattice, specifically the lengths of the cell edges and the angles between them.

Lattice EnergyLattice energy is the energy per ion pair required to separate completely the ions in a crystal lattice at a temperature of absolute zero.

Lattice ParameterThe combination of unit cell edge lengths and interaxial angles that defines the unit cell geometry.

Law of Conversation of EnergyIt states that energy cannot be destroyed nor created, but only changed in form. Ex. heat electricity light, etc.

Law of Conversation of MatterIt states that matter cannot be created nor destroyed, but only changed in form. For example matter and mass can be interchanged.

Law of Multiple ProportionsIt shows that some compounds have formulas that are whole number multiples of atoms Eg. NO2, N2O4; H2O, H2O2; FeO, Fe2O3.

LDOSee Light Diesel Oil

Le Chatelier’s PrincipleThe idea that a system at equilibrium will respond to a stress placed upon it in such a manner as to partially offset that stress. The principle was first stated in 1888 by French physical chemist Henri Le Chatelier (1850-1936).

ORStates that a system at equilibrum will oppose any change in the equilibrium conditions.

LeachateA liquid generated in landfills. It is the result of water seeping into and through the wastes. As the water contacts the waste materials it dissolves part of the organic and inorganic matter contained in the landfill. If this leachate is allowed to exit the bottom of the landfill, it will carry contaminants to the groundwater and/or adjoining surface water.

LeachingThe act of dissolving the soluble portion of a solid mixture by some solvent. An example is the dissolving of inorganic or organic contaminants from refuse in a landfill by infiltrating rain water.

Leakage RateThe maximum rate at which a fluid is permitted or determined to leak through a seal. The type of fluid, the differential Limits of Error: A tolerance band for the thermal electric

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response of thermocouple wire expressed in degrees or percentage defined by ANSI specification MC-96.1 (1975).

Lever RuleMathematical expression whereby the relative phase amounts in a two-phase alloy at equilibrium my be computed.

Lewis AcidLewis acid is an agent capable of accepoting a pair of electrons to form a coordinate bond.

Lewis BaseLewis base is an agent capable of donating a pair of electrons to form a coordinate bond.

Lewis StructuresA way of representing molecular structures based on valence electrons.

LigandLigand is an ion (F-, Cl-, Br-, I-, S2-, CN-, NCS-, OH-, NH2

-) or molecule (NH3, H2O, NO, CO) that donates a pair of electron to a metal atom or ion in forming a coordination complex.

ORThe ion or molecule which surrounds or complexes with the central atom or ion.

Ligand Field TheoryLigand field theory is a description of the structure of crystals containing a transition metal ion surrounded by nonmetallic ions (ligands). It is based on construction of molecular orbitals involving the d-orbitals of the central metal ion and combinations of atomic orbitals of the ligands.

LightIt has both wave and particle properties.

Light Diesel Oil Light Diesel Oil also known as LDO is consumed by stationary and marine diesel engines, as installed in ships or used for electricity generation.

Light YearLight year (ly) is a unit of distance used in astronomy, defined as the distance light travels in one year in a vacuum (ly = 9.46052973∙1015).

LigninsLignins are macromolecular constituents of wood related to lignans, composed of phenolic propylbenzene skeletal units, linked at various sites and apparently randomly.

Limiting ReactantThe reactant that will be exhausted first.

LimnologyThe study of freshwater ecosystems.

LinearityThe closeness of a calibration curve to a specified straight line. Linearity is expressed as the maximum deviation of any calibration point on a specified straight line during any one calibration cycle.

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LipidsLipids are a loosely defined term for substances of biological origin that are soluble in nonpolar solvents. They consist of saponifiable lipids, such as glycerides (fats and oils) and phospholipids, as well as nonsaponifiable lipids, principally steroids.

ORA naturally occurring substance soluble in organic solvents but not in water.

ORFatty Acids are together known as Lipids

Liquefied Petroleum Gas LPG (Liquid Petroleum Gas) is a mixture of short hydrocarbons with most of the volume being propane and butane. LPG is considered an alternative fuel that burns cleaner than gasoline.

ORLiquefied Petroleum Gas, known as LPG or LP Gas, is the term applied to a mixture of certain light hydrocarbons, derived from petroleum which are gaseous at normal ambient temperature and atmospheric pressure, but condensed to the liquid state at ambient temperature by application of moderate pressure. Although they are normally used as gases, they are stored and transported as liquids under pressure. Main constituents of LPG are saturated and unsaturated hydrocarbons in the C3 and C4 range (Propane, Propylene, n-Butane, iso-Butane, Butylene) and traces of Ethane, Ethylene, Pentane and Pentene are also present. LPG is used as domestic fuel, a industrial fuel, a fuel for I.C. engine, winterizing gasoline and a feedstock for the manufacture of various chemicals and olefins.

LiterLiter (l, L) is a synonym for cubic decimeter (L = dm3).

LithosphereLithosphere is the outer layer of the solid earth, extending from the base of the mantle to the surface of the crust.

Log Mean Temperature DifferenceΔTlm = (ΔT2 – ΔT1)/ [ln (ΔT2/ΔT1)]

WhereΔT1 = Th1 – Tc2

ΔT2 = Th2 – Tc1

Logarithmic ScaleA method of displaying data (in powers of ten) to yield maximum range while keeping resolution at the low end of the scale.

LPGSee Liquified Petroleum Gas

Lubricating OilsOils used for lubricating the bearing parts of machinery. They are usually the heavy distillate in the fractional distillation of petroleum. Depending upon their molecular weights they are classified into grades as light, medium, and heavy lubricating oils. Their boiling point ranges from 200°C to 350°C.

LumenLumen (lm) is the SI derived unit of luminous flux. The lumen is the luminous flux emitted in a solid angle of one steradian by a point source having a uniform intensity of one candela (1lm =1 cd∙sr).

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Luminous FluxLuminous flux (Φ) is the intensity of light from a source multiplied by the solid angle. The SI unit is lumen.

LuxLux (lx) is the SI derived unit of illuminance. The lux is the illuminance produced by a luminous flux of one lumen uniformly distributed over a surface of one square metre (lx = lm·m-2).

Lyman SeriesLyman series is the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the ground state (principal quantum number n = 1) and successive excited states.

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MMMega; one million.

MacromoleculeMacromolecule is a molecule of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass.

ORA huge molecule made up of thousands of atoms.

MagmaMolten or partially molten rock at temperatures ranging from 1,260 F to 2,880 F (700 C to 1600 C). Some magma bodies are believed to exist at drillable depths within the Earth's crust, although practical technologies for harnessing magma energy have not been developed. If ever utilized, magma represents a potentially enormous resource.

MartensiteA metastable Fe-C composition consisting of supersaturated carbon in iron that is the product of a diffusionless (athermal) transformation from austenite.

MassMass (m) is the quantity of matter contained in a particle or body regardless of its location in the universe. Mass is constant, whereas weight is affected by the distance of a body from the center of the Earth (or of other planet). The SI unit is kilogram.According to the Einstein equation

E = mc2

All forms of energy possess a mass equivalent.

Mass balanceAn organized accounting of all inputs and outputs to an arbitrary but defined system. Stated in other terms, the rate of mass accumulation within a system is equal to the rate of mass input less the rate of mass output plus the rate of mass generation within the system.

Mass Flow RateVolumetric flowrate times density, i.e. pounds per hour or kilograms per minute.

Mass FractionMass fraction (wA) is the ratio of the mass of substance A to the total mass of a mixture.

WA = mA / ∑mi

Mass NumberMass number (A) is a characteristic property of a specific isotope of an element, equal to the sum of the number of protons and neutrons in the nucleus.

ORMass Number is the relative mass of the isotopes compared to that of Carbon-12 whose mass is 12.0000 g/mol. It is not shown on the periodic chart. It is also equal to the sum of protons + neutrons inasmuch as protons and neutrons each have an atomic mass of 1 g/mol (amu - atomic mass unit).

ORThe number of protons and neutrons in an atom.

OR

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The sum of the number of neutrons and protons in a nucleus.

Mass SpectrometerIt is a refined Sir JJ Tube in which the masses of particles, ions, and isotopes are measured. It separates isotopes according to charge and mass.

Mass SpectrometryMass spectrometry is an analytical technique in which ions are separated according to the mass/charge (m/e) ratio and detected by a suitable detector.

In a mass spectrometer a sample is ionized and the positive ions produced are accelerated into a high-vacuum region containing electric and magnetic fields. These fields deflect and focus the ions onto a detector. A mass spectrum is thus obtained consisting of a series of peaks of variable intensity to which m/e values can be assigned. Different molecules can be identified by their characteristic pattern of lines.

MatrixThe body constituent of a composite or two-phase alloy that completely surrounds the dispersed phase and gives the body its bulk form.

Maximum Contaminant LevelThe maximum allowable concentration of a given constituent in potable water.

Maximum Operating TemperatureThe maximum temperature at which an instrument or sensor can be safely operated.

MCLSee Maximum Contaminant Level

Mean Free PathMean free path is the average distance a gas molecule travels between collisions.

Mean Ionic Activity CoefficientSee Activity coefficient.

Mean TemperatureThe average of the maximum and minimum temperature of a processequilibrium.

MeasurandA physical quantity, property, or condition which is measured.

Measuring JunctionThe thermocouple junction referred to as the hot junction that is used to measure an unknown temperature.

Mechanical HysteresisThe difference of the indication with increasing and decreasing strain loading, at identical strain values of the specimen.

Medium EffectFor solvents other than water the medium effect is the activity coefficient related to the standard state in water at zero concentration. It reflects differences in the electrostatic and chemical interactions of the ions with the molecules of various solvents. Solvation is the most significant interaction.

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Meissner EffectMeissner effect is the complete exclusion of magnetic induction from the interior of a superconductor.

Melting PointMelting point (or freezing point) is the temperature at which the solid and liquid phases of a substance are in equilibrium at a specified pressure (normally taken to be atmospheric unless stated otherwise). A pure substance under standard condition of pressure has a single reproducible melting point. The terms melting point and freezing point are often used interchangeably, depending on whether the substance is being heated or cooled.

ORThe temperature at which a substance transforms from a solid phase to a liquid phase.

ORThese are caused by the van der waals interaction. Solids melt and liquids evaporate when the van der waals forces between molecules are broken.

ORThe temperature at which a solid substance changes to liquid state

ORThe temperature at which a solid substance changes to a liquid state.

MembraneThe pH-sensitive glass bulb is the membrane across which the potential difference due to the formation of double layers with ion-exchange properties on the two swollen glass surfaces is developed. The membrane makes contact with and separates the internal element and filling solution from the sample solution.

MeniscusMeniscus is the concave curve of a liquid surface in a graduate or narrow tube. Caused by surface tension.

MerThe group of atoms that constitutes a polymer chain repeat unit.

MercaptansMercaptans are a traditional term abandoned by IUPAC, synonymous with thiols. This term is still widely used.

ORA group of inflammable, organic compounds containing –SH group, analogous to the monohydric alcohols. Mercaptans are also termed as thioalcohols and sulphur-alcohols. The more general term thiols, is also used. They have a very sharp, unpleasant (garlic like) odour, are insoluble in water, but soluble in alcohol. They may be prepared by several methods; for example, by heating ethyl alcohol with phosphorus pentasulphide, the oxygen being thus replaced by sulphur; or by heating a mixture of an alkali halide with potassium hydrosulphide. The thio ethers or dialkyl sulphides, such as ethyl sulphide (C2H5)S are neutral volatile liquids devoid of acid character. Since they have objectionable odour, they are sometimes added to odourless gases (such as natural gas and LPG) to give rapid warning of a leak. The unpleasant smell associated with oil refineries is partly due to mercaptans. They are sometimes called thiols. Mercaptans may be produced in oil refinery feed preparation units as a result of incipent cracking; th offensive gases are burnet in plant heaters. Mercaptans arising in cracking units are usually removed by scrubbing with caustic soda, the mercaptans being removed from the spent caustic soda by stream stripping and subsequently burned in a process furnace. Also known as thioalcohols.

ORSee thiols.

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MetabolismThe processes which sustain an organism, including energy production, synthesis of proteins for repair and replication.

MetalMetals are a material in which the highest occupied energy band (conduction band) is only partially filled with electrons.

Their physical properties generally include:- They are good conductors of heat and electricity. The electrical conductivity

of metals generally decreases with temperature.- They are malleable and ductile in their solid state.- They show metallic luster.- They are opaque.- They have high density.- They are solids (except mercury)- They have crystal structure in which each atom is surrounded by eight to

twelve near neighbors

Their chemical properties generally are:- They have one to four valence electrons.- They have low ionization potentials; they readily lose electrons.- They are good reducing agents.- They have hydroxides which are bases or amphoteric.- They are electropositive.

Metallic characteristics of the elements decrease and non-metallic characteristics increase with the increase of valence electrons. Also metallic characteristics increase with the number of electron shells. Therefore, there is no sharp dividing line between the metals and the non-metals.

Of the 113 elements now known, only 17 show primarily non-metallic characteristics, 7 others are metalloids, and 89 may be classed as metals.

MetalimnionThe middle layer of a lake.

MetalloidMetalloid (semimetal) is any of a class of chemical elements intermediate in properties between metals and nonmetals. The classification is not clear cut, but typical metalloids are boron (B), silicon (Si), germanium (Ge), arsenic (As), and tellurium (Te). They are electrical semiconductors and their oxides are amphoteric.

MetastableNonequilibrium state that may persist for a very long time.

MeteorologyThe study of the atmosphere and weather of the lower atmosphere, below 100 km.

Methods of IonizationThese include photoionization (using light energy like ultraviolet rays), thermionic emission (using high temperature to boil off electrons), and electron bombardment (kick 'em out with a stream of electrons from another source).

Methyl Tertiary Butyl EtherMethyl Tertiary Butyl Ether (MTBE) is an ether compound used as a gasoline blending component to raise the oxygen content of gasoline. MTBE is made by combining isobutylene

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(from various refining and chemical processes) and methanol (usually made from natural gas).

MetreMetre (m) is the SI base unit of length.The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 s.

This definition, adopted by the General Conference on Weights and Measure in October 1983, replaced the 1967 definition based on the krypton lamp.

MhoMho is an archaic name for the SI unit siemens (reciprocal ohm).

MicaA transparent mineral used as window material in high-temperature ovens.

MicelleMicelle is an electrically charged colloidal particle, usually organic in nature, composed of aggregates of large molecules, e.g., in soaps and surfactants. For aqueous solutions, the hydrophilic end of the molecule is on the surface of the micelle, while the hydrophobic end (often a hydrocarbon chain) points toward the center.

MicronMicron (μ) is an obsolete name for micrometer (μm).

OROne millionth of a meter, 10-6 meters.

MicrostructureThe structural features of an alloy that are subject to observation under a microscope.

Millikan Oil Drop ExperimentThis Experiment measured the actual charge on an electron.

MillimeterOne thousandth of a meter, symbol mm.

Millimeter of MercuryMillimeter of mercury (mmHg) is a non-SI unit of pressure, equal to 133.322 Pa. The name is generally considered interchangeable with torr.

Mineral-insulated ThermocoupleA type of thermocouple cable which has an outer metal sheath and mineral (magnesium oxide) insulation inside separating a pair of thermocouple wires from themselves and from the outer sheath. This cable is usually drawn down to compact the mineral insulation and is available in diameters from .375 to .010 inches. It is ideally suited for high-temperature and severe-duty applications.

Mixed Liquor Suspended SolidsThe total suspended solids concentration in the activated sludge tank.

Mixed Liquor Volatile Suspended SolidsThe volatile suspended solids concentration in the activated sludge tank.

MixtureComposed of two or more substances, but each keeps its original properties.

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MLSSSee Mixed Liquor Suspended Solids.

MLVSSSee Mixed Liquor Volatile Suspended Solids.

Modulus of ElasticityThe ratio of stress to strain for a material under perfectly elastic deformation.

MoistureThe water content of a substance (a solid fuel) as measured under specified conditions being the: Dry Basis, which equals the weight of the wet sample minus the weight of a (bone) dry sample divided by the weight of the dry sample times 100 (to get percent); Wet Basis, which is equal to the weight of the wet sample minus the weight of the dry sample divided by the weight of the wet sample times 100.

MolalityMolality or molal concentration (b; formerly m) is a concentration in which the amount of solute is stated in moles and the amount of solvent in kilograms.

The unit of molality is mol kg-1.OR

A measure of concentration expressed in mols per kilogram of solvent. OR

The number of moles of solute (the material dissolved) per kilogram of solvent (what the solute is dissolved in).

MolarDenoting that an extensive physical property is being expressed per amount of substance, usually per mole.

ORAn term expressing molarity, the number of moles of solute/ liters of solution

Molar MassMolar mass is the mass of one mole of a substance.

M = m/nIt is normally expressed in units of g mol-1, in which case its numerical value is identical with the relative molecular mass.

Molar QuantityMolar quantity is often convenient to express an extensive quantity (e.g., volume, enthalpy, heat capacity, etc.) as the actual value divided by amount of substance (number of moles). The resulting quantity is called molar volume, molar enthalpy, etc.

Molar VolumeMolar volume is the volume occupied by substance per unit amount of substance. The volume of the gas at 0 °C and 101 325 Pa is 22.4 dm3mol-1.

MolarityFormerly name for concentration.

ORThe number of moles of solute (the material dissolved) per liter of solution. Used to express the concentration of a solution.

MoleMole (mol) is the SI base unit of amount of substance.

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The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kg of carbon 12.

When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particules, or specified groups of such particles. In this definition, it is understood that the carbon 12 atoms are unbound, at rest and in their ground state.

ORA collection of 6.023* 1023 number of objects. Usually used to mean molecules.

ORMole is the number of atoms in the atomic mass of an element or the number of molecules in the molecular mass of a compound. It = 6.02 X 10 to the 23 atoms or molecules.

Mole FractionMole fraction (xA) is the ratio of the amount of substance (number of moles) of substance A to the total amount of substance in a liquid mixture or solution.

xA = nA/∑ni

ORThe number of moles of a particular substance expressed as a fraction of the total number of moles.

Molecular FormulaIt shows the actual number of atoms in compound. Ex. C2H4

ORShows the number of atoms of each element present in a molecule.

Molecular GeometryShape of a molecule, based on the relative positions of the atoms.

Molecular MassIt is the sum of the atomic masses of all the atoms in a molecule.

Molecular WeightThe combined weight (as given on the periodic table) of all the elements in a compound.

ORSee Relative molecular mass

MoleculeMolecule is the smallest part of a chemical compound that can take part in a chemical reaction. The atoms of a molecule are held together by chemical bonds.

ORIt is the smallest particle of a chemical compound. It contains two or more atoms.

ORTwo or more atoms chemically combined.

ORA molecule is two or more atoms joined together by chemical bonds. This may result in two atoms of the same molecule, such as chlorine, Cl2, or by combining elements as in ammonia, NH3. A molecule can be considered the smallest unit representitve of that compound which possesses all its properties.

MomentumMomentum (p) is the product of mass and velocity (p = m∙v).

MonomerMonomer is a simple molecule which is capable of combining with a number of like or unlike molecules to form a polymer. Monomer is repeating structure unit within a polymer.

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ORA molecule consisting of a single mer.

MonosaccharideMonosaccharide is a charbohydrate that cannot be split into smaller units by the action of dilute acids.Monosaccharide is any of several simple sugars having the formula C6H12O6; the best-known are glucose, fructose, and galactose. Monosaccharides combine to form more-complex sugars known as oligo- and polysaccharide.

Monovalent IonAn ion with a single positive or negative charge (H+, Cl-).

MTBESee Methyl Tertiary Butyl Ether

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NNaphthaNaphtha is the generic name given to the light hydrocarbons boiling in the gasoline range. It is obtained during distillation within a temperature range 40 – 240°C and is composed of hydrocarbons ranging from C5 to C13. Depending upon the boiling points of hydrocarbons, naphthas are classified as light naphtha (boiling below 100°C), intermediate naphtha (boiling between 100 - 150°C), and heavy naphtha (boiling above 150°C). Naphtha finds an extensive use as fertilizer feedstock, and in fertilizer industries. It is also used as commercial solvents, as thinner for paints, varnishes and lacquers, and in benzene, toluene, and xylene manufacture.

Natural ConvectionSee Free Convection

Natural DraftDraft that is caused by temperature differences in the air.

Natural GasA hydrocarbon gas obtained from underground sources, often in association with petroleum and coal deposits. It generally contains a high percentage of methane, varying amounts of ethane, and inert gases; used as a heating fuel.

ORIt is a mixture of combustible gases, that occur in porous rocks and is found with or near accumulation of crude oil. Typical natural gas consists of hydrocarbons having a very low boiling point. Methane is the major constituent of natural gas (upto 85 %). Ethane may be present upto 10 % and propane upto 3 %, while butane, pentane, hexane, heptane, octane, CO2, nitrogen, helium and hydrogen may also be present in traces. It is also present in liquid form as LNG. It is an important source of synthesis gas, used in making synthetic organic materials and natural gasoline. It can also be made synthetically (synthetic natural gas) from petroleum fractions such as naphtha and by gasification of coal.

Natural Gas Steam ReformingA two step process where in the first step natural gas is exposed to a high-temperature steam to produce hydrogen, carbon monoxide, and carbon dioxide. The second step is to convert the carbon monoxide with steam to produce additional hydrogen and carbon dioxide.

Nautical MileNautical mile is a legal international unit of length temporarily maintained with the SI. It is still used in navigation (mercantile marine, aviation). It is equal to the length of an arc of one minute measured at a latitude of N45° (mile = 1852 m). The international nautical mile has been taken equal to the nautical mile.

Néel Temperature Néel temperature (TN) is the critical temperature above which an antiferromagnetic substance becomes paramagnetic. The phenomenon was discovered around 1930 by L.E.F. Néel (1904- ).

NeopreneNeoprene is a synthetic ruber made by polimerizing the compound 2-chlorobuta-1,2-diene. Neoprene is often used in place of natural rubber in applications requiring resistance to chemical attack.

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Nernst EquationA mathematical description of electrode behavior: E is the total potential, in millivolts, developed between the sensing and reference electrodes; Ex varies with the choice of electrodes, temperature, and pressure: 2.3RT/nF is the Nernst factor (R and F are constants, n is the charge on the ion, including sign, T is the temperature in degrees Kelvin), and ai is the activity of the ion to which the electrode is responding.

Nessler’s ReagentNessler's reagent is a solution of mercury(II) iodide (HgI2) in potassium iodide and potassium hydroxide named after Julius Nessler (1827-1905). It is used in testing for ammonia, with which it forms a brown coloration or precipitate.

Net Positive Suction Head The Net Positive Suction Head (NPSH) is the total suction head in metres of liquid (absolute at the pump centreline or impeller eye) less the absolute vapour pressure (in metres) of the liquid being pumped. It must always have a positive value.

ORNet  positive  suction  head  (NPSH)  for  a  pump  is  the difference between the suction pressure and the saturation pressure of the fluid being pumped. NPSH is used to measure how close a fluid is to saturated conditions. The units of NPSH are feet of water.

NPSH = Psuction - Psaturation

where:Psuction = suction pressure of the pump Psaturation = saturation pressure for the fluid

Network PolymerA polymer composed of trifunctional mer units that form three-dimensional molecules.

NeutralAn object that does not have a positive or negative charge.

NeutralizationNeutralization is the process in which an acid reacts with a base to form a salt and water.

H+ + OH- ⇌ H2O

NeutrinoNeutrino is a stable elementary particle in the lepton family. Neutrinos have zero (or at least near-zero) rest mass and spin 1/2.

NeutronNeutron is an elementary particle on spin 1/2 and zero charge. The free neutron has a mean lifetime of 887 seconds. Neutrons and protons, which are collectively called nucleons, are the constituents of the nucleus.

ORNeutron is a basic particle whose charge is 0 and whose mass is 1 g/mol (amu).

ORA particle found in the nucleus of an atom. It is almost identical in mass to a proton, but carries no electric charge.

OROne of the three fundamental particles which form atoms, the neutron has the mass of a proton but no electrical charge. Neutrons are emitted when large atomic nuclei are bombarded with alpha particles.

Neutron Number

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Neutron number (N) is a characteristic property of a specific isotope of an element, equal to the number of neutrons in the nucleus.

NewtonNewton (N) is the SI unit of force, being the force required to give a mass of one kilogram an acceleration of 1 m s-2 (N = kg m s-2). It is named after British scientist Sir Isaac Newton (1642-1727).

ORAfter Sir Isaac Newton, English (1642-1727). The newton is a unit of force. Thus, 1 newton equals the force with which a mass of 101.97 grams presses downward under standard gravitational conditions on earth. And a mass of 1 kilogram presses down with a force of 9.80665 newtons.

NitrificationThe biological oxidation of ammonia and ammonium sequentially to nitrite and then nitrate. It occurs naturally in surface waters, and can be engineered in wastewater treatment systems. The purpose of nitrification in wastewater treatment systems is a reduction in the oxygen demand resulting from the ammonia.

Nitrogen fixationThe conversion of atmospheric (or dissolved) nitrogen gas into nitrate by microorganisms.

Nitrogenous Oxygen DemandThe amount of oxygen required to oxidize any ammonia present in a water.

nmAn abbreviation for nano-meters. A nano-meter is equal to 10-9 meters.

NMRSee Nuclear Magnetic Resonance

Noble GasNoble gas refers to any element of the group of six elements in group 18 of the periodic table. They are helium (He), neon (Ne), argon (Ar), krypton (Kr) , xenon (Xe), and radon (Rn). Unlike most elements, the noble gases are monoatomic. The atoms have stable configurations of electrons. Therefore, under normal conditions they do not form compounds with other elements.

They were generally called inert gases until about 1962 when xenon tetrafluoride, XeF4 was produced in the laboratory. This was the first report of a stable compound of a noble gas with another single element.

ORThis collection of elements make up Group 0 in the periodic table. They were known as inert gases for many years but that has changed with the reports of noble gas compounds. They are all gaseous elements found in the atmosphere, except for radon which is formed from the radioactive decay of uranium. The elememts are inert due to their stable electronic configuration. The gases are useful as inert atmospheres for reactions that must exclude oxygen, for balloons (helium) and for lighting displays.

NODSee Nitrogenous Oxygen Demand

Non-CombustibleA material which will not ignite, burn or support combustion when subjected to heat or fire.

Non-Metals

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Non-metals are defined as elements that are not metals.Their physical properties generally include:- They are poor conductors.- They are brittle, not ductile in their solid state.- They show no metallic luster.- They may be transparent or translucent.- They have low density.- They form molecules which consists of atoms covalently bonded; the noble

gases are monoatomic.Their chemical properties are generally:

- They usually have four to eight valence electrons.- They have high electron affinities (except the noble gases)- They are good oxidizing agents (except the noble gases)- They have hydroxides which are acidic (except the noble gases)- They are electronegative.

Non-crystallineThe solid state wherein there is no long-range atomic order. Sometimes used synonymously with the terms amorphous, glassy and vitreous.

Nonpoint Source PollutionAny pollution from a source which cannot be attributed to a particular discharge point, e.g. from agricultural crops, city streets, construction sites, etc.

Normal (axial) StressThe force per unit area on a given plane within a body a = F/A

Normal Hydrogen ElectrodeA reversible hydrogen electrode (Pt) in contact with hydrogen gas at 1 atmosphere partial pressure and immersed in a solution containing hydrogen ions at unit activity.

NPDESThe National Pollutant Discharge Elimination System. The discharge criteria and permitting system established by the U.S. EPA as a result of the Clean Water Act and its subsequent amendments or the permit required by each discharger as a result of the Clean Water Act.

NPSHSee Net Positive Suction Head.

NPSPSee Nonpoint Source Pollution

NPTNational Pipe Thread.

NSRSee Nuclear Science Reference

Nuclear Magnetic ResonanceNuclear magnetic resonance (NMR) is a type of radio-frequency spectroscopy based on the magnetic field generated by the spinning of electrically charged atomic nuclei. This nuclear magnetic field is caused to interact with a very large (1 T - 5 T) magnetic field of the instrument magnet. NMR techniques have been applied to studies of electron densities and chemical bonding and has become a fundamental research tool for structure determinations in organic chemistry.Nuclear Reactor

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Nuclear reactor is an assembly of fissionable material (uranium-235 or plutonium-239) designed to produce a sustained and controllable chain reaction for the generation of electric power. The essential components of a nuclear reactor are:

1. The core, metal rods containing enough fissionable material to maintain a chain reaction at the necessary power level (as much as 50 t of uranium may be required).

2. A source of neutrons to initiate the reaction (such as a mixture of polonium and beryllium)

3. A moderator to reduce the energy of fast neutrons for more efficient fission (material such as graphite, beryllium, heavy water, and light water are used)

4. A coolant to remove the fission-generated heat (water, sodium, helium, and nitrogen may be used)

5. A control system such as rods of boron or cadmium that have high capture cross sections (to absorbs neutrons)

6. Adequate shielding, remote-control equipment, and appropriate instrumentation are essential for personnel safety and efficient operation.

NucleationThe initial stage in a phase transformation. It is evidenced by the formation of small particles (nuclei) of the new phase, which are capable of growing.

Nucleic AcidNucleic acids are macromolecules (relative molecular mass over 5 000 000), the major organic matter of the nuclei of biological cells, made up of nucleotide units, and hydrolyzable into certain pyrimidine or purine bases (usually adenine, cytosine, guanine, thymine, uracil), D-ribose or 2-deoxy-D-ribose.

NucleonNucleon is a collective term for the proton and neutron.

ORIt refers to the particles in the nucleus - Protons and Neutrons.

ORA proton or neutron.

NucleusThe central part of an atom that contains the protons and neutrons. Plural nuclei.

ORThe core of the atom, where most of its mass and all of its positive charge is concentrated. Except for hydrogen, it consists of proton and neutrons.

NuclideNuclide is a species of atoms in which each atom has identical atomic number Z and identical mass number A.

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OOctahedral PositionThe void space among closed-packed, hard sphere atoms or ions for which there are six nearest neighbors. An octahedron (double pyramid) is curcumscribed by lines constructed from centers of adjacent spheres.

Octane NumberAn arbitrary value denoting the antiknocking rating of gasoline fuel: it is the proportion of the branched chain hydrocarbon iso-octane, that is contained in a test mixture of heptane and iso-octane. The octane number of heptane (a straight-chain hydrocarbon) is rated as zero, while that of iso-octane is 100. Also known as Octane rating.

ORA unit of measurement on a scale intended to indicate the tendency of a fuel to detonate or knock based on the percentage of isooctane in the fuel. The higher the rating, the higher the percentage of isooctane and therefore the greater the resistance to detonation offered by the fuel.

Octane RatingSee Octane Number

OctetIn Lewis structures the goal is to make almost all atoms have an octet. This means that they will have access to 8 electrons regularly, even if they do have to share some of them.

O.D.Outside diameter.

OerstedOersted (Oe) is a non-SI unit of magnetic field (H), equal to 79.57747157 A/m. The unit is named after the H.C. Oersted (1777-1851).

OffsetThe difference in temperature between the set point and the actual process temperature. Also, referred to as droop.

OFHCSee Oxygen-Free High-Conductivity Copper

OhmOhm (W) is the SI derived unit of electric resistance. The ohm is the electric resistance between two points of a conductor when a constant difference of potential of one volt, applied between these two points, produces in this conductor a current of one ampere, this conductor not being the source of electromotive force (W = V/A). The unit is named after the German physicist Georg Simon Ohm (1789-1854).

ORAfter Georg Simon Ohm, German (1787-1854). The ohm is a unit of electricalresistance.

OlefinsOlefins are acyclic and cyclic hydrocarbons having one or more carbon-carbon double bonds, apart from the formal ones in aromatic compounds. The class olefins subsumes alkenes and cycloalkenes and the corresponding polyenes.

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OligomerOligomer is a substance consisting of molecules of intermediate relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. In contrast to a polymer, the properties of an oligomer can vary significantly with the removal of one or a few of its units.

Onsager RelationshipOnsager relations are an important set of equations in the thermodynamics of irreversible processes. They express the symmetry between the transport coefficients describing reciprocal processes in systems with a linear dependence of flux (Ji) on driving forces (Xj).

Ji = ∑m j =1 Lij Xj

In Onsager's theory the coupling coefficients are equal, Lij = Lji. This are known as reciprocal relations. The theory was developed by the Norwegian chemist Lars Onsager (1903-1976) in 1931.

Operational pHThe determination of sample pH by relating to pH measurements in a primary standard solution. This relationship assumes that electrode errors such as sensitivity and changes in asymmetry potential can be disregarded or compensated for, provided the liquid junction potential remains constant between standard and sample.

OrbitalOrbital is the area in space about an atom or molecule in which the probability of finding an electron is greatest.

The possible atomic orbitals correspond to subshells of the atom. Thus there is one s-orbital for each shell (orbital quantum number l = 0). There are three p-orbitals (corresponding to the three values of l) and five d-orbitals. The shapes of orbitals depend on the value of l.

ORAn energy state in the atomic model which describes where an electron will likely be.

Organic ChemicalsOrganic chemicals are based on carbon compounds.

Organic compoundAny compound containing carbon except for the carbonates (carbon dioxide, the carbonates and bicarbonates), the cyanides, and cyanates.

Organic nitrogenNitrogen contained as amines in organic compounds such as amino acids and proteins.

OsmosisOsmosis is the flow of a solvent in a system in which two solutions of different concentration are separated by a semipermeable membrane which cannot pass solute molecules. The solvent will flow from the side of lower concentration to that of higher concentration, thus tending to equalize the concentrations. The pressure that must be applied to the more concentrated side to stop the flow is called the osmotic pressure.

Osmotic PressureOsmotic pressure (Π) is the excess pressure necessary to maintain osmotic equilibrium between a solution and the pure solvent separated by a membrane permeable only to the solvent. In an ideal dilute solution

Π = cB RT

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where cB is the amount-of-substance concentration of the solute, R is the molar gas constant, and T the temperature.

Ostwald ProcessA method for the preparation of nitric acid from ammonia by its oxidation successively to nitric oxide, nitrogen dioxide, and finally nitric acid, using elevated temperatures and platinum gauze as a catalyst

Ostwald RuleWhen a substance can exist in more than one form, reactions for its production usually yield the least stable modification, which subsequently undergoes a process of transformation until the most stable form is reached.

Ostwald’s Dilution LawFormula which describes classical electrolytic dissociation constant Kc

Kc = (Λc2c) / (Λo - Λc)Λc

Where Λc & Λc = equivalent conductivity of infinitely diluted electrolyte and electrolyte at concentration c respectively; Ostwald’s dilution law applies approximately to diluted solutions of weak electrolytes.

Othmer ProcessA process for the production of pure acetic acid from crude pyroligneous acid, the crude liquor is distilled, and the vapour is passed through purifying columns, in which the methanol, acetone, tar, and other components are removed by absorption, or solution. The vapours of acetic acid and water then pass to condenser.

OverpotentialOverpotential (η) is a potential that must be applied in an electrolytic cell in addition to the theoretical potential required to liberate a given substance at an electrode. The value depends on the electrode material and on the current density.

OvershootThe number of degrees that a process exceeds the set point temperature when coming up to the set point temperature.

OxidationThe term oxidation originally meant a reaction in which oxygen combines chemically with another substance. More generally, oxidation is a part of a chemical reaction in which a reactant loses electrons (increase oxidation number). Simultaneous reduction of a different reactant must occur (redox reaction).

ORA reaction where a substance loses electrons

ORThis is a reaction with oxygen, as in combustion. An oxidized molecule is generally one that has lost electrons. Reduction also takes palce during oxidation - if one substance is oxidised then anothr must be reduced.

Oxidation NumberIt is the number of electrons lost, gained or shared in a chemical reaction. Free elements have zero as an oxidation number. Also known as valence.

ORA number assigned to each atom to help keep track of the electrons during a redox-reaction.

Oxidation-Reduction ReactionA reaction involving the transfer of electrons.

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Oxidative PhosphorylationThe synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP) using a chemical substrate and molecular oxygen.

OximesOximes are organic compounds of structure R2C=NOH derived from condensation of aldehydes or ketones with hydroxylamine. Oximes from aldehydes may be called aldoximes; those from ketones may be called ketoximes.

Oxo CompoundsOxo compounds are organic compounds that contain the karbonyl group, C=O. The term thus embraces aldehydes, carboxylic acids, ketones, amides, and esters.

Oxy AcidWhen one or more hydroxide (OH) groups are bonded to a central atom.

Oxygen-Free High-Conductivity Copper The industrial designation of the pure copper used in a Type T thermocouple.

OzoneOzone is an alotropic form of oxygen. It is unstable blue gas with pungent odor. It is a powerful oxidizing agent. The gas is made by passing oxygen through a silent electric discharge.

3O2(g) ⇌ 2O3(g)

Ozone DepletionChemical destruction of the stratospheric ozone layer over and above natural processes.

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PP-type SemiconductorA semiconductor for which the predominant charge carriers responsible for electrical conduction are holes. Normally, acceptor impurity atoms give rise to the excess holes.

Packed TowerSee trickling filter.

ParaffinsParaffins are obsolescent term for alkanes. Still widely used in the petrochemical industry.

ORSee Alkanes

Parts Per Million100 ppm is identical to 0.01%.

Pair ProductionA collision process for gamma rays with energies greater than 1022-keV (two electron masses) where an electron /positron pair is produced. A heavy nucleus must be present for pair production. For high-energy gamma rays the pair production process is proportional to Z2 and ln(gamma).

Paraffin WaxA thermoplastic solid of high molecular weight, which is a hydrocarbon derived from distillation of an aliphatic petroleum (Paraffin Wax). Waxes are physically plastic, but are sensitive to temperature. It is used for making candles, waxed papers, for match stick coating, rust prevention etc.

ParamagnetismParamagnetism is a type of magnetism characterized by a positive magnetic susceptibility, so that the material becomes weakly magnetized in the direction of an external field. The magnetization disappears when the field in removed.

ORA relatively weak form of magnetism that results from the independent alignment of atomic dipoles (magnetic) with an applied magnetic field.

Parent IsotopeAn element that undergoes nuclear decay.

ParityA nucleus or particle has odd (-) or even (+) parity according to whether or not its wave function changes sign when all of the space coordinates are changed.

Partial PressureThe pressure exerted by a certain gas in a mixture.

ORThe partial pressure of a component gas that is present in a mixture of gases is the pressure that would be exerted by that component if it alone were present in the same volume and at the same pressure.

ParticleSmall portion of matter

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Paschen SeriesPaschen series are the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the state with principal quantum number n = 3 and successive higher states.

Pathogenic OrganismAn organism capable of causing infection.

Pauli Exclusion PrinciplePauli exclusion principle is the statement that two electrons in an atom cannot have identical all four quantum numbers. It was first formulated in 1925 by Austrian-born Swiss physicst Wolfgang Ernst Pauli (1900-1958).

ORIt states that no two electrons may have the same quantum numbers. Only two electrons may occupy an orbital, but they must have opposite spins.

PearliteA two-phase microstructure found in some steels and cast irons. It results from the transformation of austenite of eutectoid compositions and consists of alternating layers of alpha-ferrite and cementite.

Peltier EffectPeltier effect is the absorption or generation of heat (depending on the current direction) which occurs when an electric current is passed through a junction between two materials.

PeptidesPeptides are amides derived from two or more amino acids (the same or different) linked by peptide bonds. These bonds are formed by the reaction between adjancent carboxyl (-COOH) i amino (-NH2) groups with the elimination of water.

ORAn organic compound containing the group -CONH (see below), examples of which are polypeptides.

Percentage Compositioncan be found by totaling the atomic masses of the atoms in the formula, dividing each mass by the total, and changing the results to %-age.

ORExpresses the weight ratio between different elements in a compound.

Periodic TablePeriodic table is a table of the elements, written in sequence in the order of atomic number or atomic weight and arranged in horizontal rows (periods) and vertical columns (groups) to illustrate the occurrence of similarities in the properties of the elements as a periodic function of the sequence. The original form was proposed by Dmitri Mendeleev (1834-1907) in 1869 using relative atomic masses.

ORFirst worked out by Mendeleev in 1869 is organized by the regularly repeating pattern of chemical properties of the elements. Each column is a family of elements having similar properties. The properties are a periodic function of the atomic numbers. Atomic number is symbolized "Z". The table is based on the electron configuration of the atoms. The first column is the Alkali metals, they react vigorously with water to give hydrogen gas. They are lithium, sodium, potassium, rubidium, cesium, and francium. Francium is a man-made radioactive element.

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The second column is the Alkaline Earth elements. They are active, but much less so than the previous column. The transition metals have electrons filling d sublevels. They, used alone or as alloys, are our principal structural metals. An alloy is a mixture of metals, a solid solution. The seventh column is the Halogens (salt formers). These are the deadly fluorine, chlorine, bromine, iodine, and astatine. Astatine is a man-made radioactive element. The eighth column is the noble gases. These loafers are most inactive. Only extreme measures can make them react. They are helium, neon, argon, krypton, xenon, and radon. The Lanthanides and Actinides are the two rows at the bottom of the chart. Each of these two series fit into one spot (Lanthanides in the the lanthanum place, and Actinides into the actinium place). The reason for this is because electrons are being added to the 4f sublevel instead of to a sublevel of the sixth or outer level. Hence they all have the same oxidation state (valence) and similar properties.

ORGrouping of the known elements by their number of protons. There are many other trends such as size of elements and electronegativity that are easily expressed in terms of the periodic table.

OREarly alchemists understood that certain elements could be grouped together due to the properties that they had. But it was not until the 18th century that Lavoisier tried to classify the known elements. It took another 100 years and a lot of trial and error for Mendeleev to propose a real foundation for the modern periodic table. He arranged the elements in a table according to relative atomic mass and left gaps where an element did not match. By doing this he could predict where a new element should come and what properties it should have.

PeriodsPeriods are horizontal rows in the periodic table. Each period beginning with an alkali metal (one electron in the outermost principal quantum level) and ending with an noble gas (each having eight electrons in the outermost principal quantum level, except for helium, which is limited to two).

PermittivityThe proportionality constant between the dielectric displacement D and the electric field E.

PeroxidesPeroxides are compounds of structure ROOR in which R may be any organic group. In inorganic chemistry, salts of the anion O2

-2. They are strong oxidizing agents.

PetrochemicalAn organic compound that has been derived from petroleum or natural gas.

PetrolSee Gasoline

PetrolatumPetrolatum, also known as Vaseline or Petroleum jelly, is a jelly like substance obtained in the fractional distillation of petroleum. It comprises a two phase colloidal system or gel consisting of high-molecular-mass hydrocarbon oils dispersed in micro crystalline waxes. Its composition lies between C17H36 to C21H44 and it boils at a temperature above 300°C. It is used for lubricating purpose and for compounding with rubber and resins.

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Petroleum CompositionA typical composition (by weight %) of petroleum is as follows :

Carbon 84.0 % - 87.0 % Hydrogen 11.0 % - 15.0%Sulfur 0.1 % - 3.0 % Nitrogen 0.1 % - 1.5 %Oxygen 0.3 % - 1.8 %

The principal compositions of petroleum are hydrocarbons. A small amount of sulfur, nitrogen and oxygen compounds are present as impurities. Some inorganic compounds and metals are also present in traces.

Sulfur compounds found in petroleum are hydrogen sulfide, thiophenes, mercaptans.

Oxygen occurs in combined form in alcohols, phenols, resins and organic acids present in petroleum.

Nitrogen compound include pyridines, quinolines, pyroles etc. Inorganic compounds present in petroleum are salt, clay, sand, etc. Metals present are vanadium, nickel, copper, iron, arsenic and platinum.

Petroleum EtherPetroleum ether is the petroleum fraction consisting of C5 and C6 hydrocarbons and boiling in the range 35 °C to 60 °C; commonly used as a laboratory solvent.

Petroleum ProductsThe petroleum refinery products are divided into six major categories :1) Gas Fraction -

Natural gas Off gases from petroleum conversion operations LPG

2) Light Ends - Petrol Or Motor Spirit Naphtha Or Solvent Spirit Kerosene

3) Intermediate Distillates - Diesel Oils Gas Oil

4) Heavy Distillates - Lubricating Oils Fuel Oils Paraffin Wax

5) Residues - Grease Petrolatum Asphalt

6) By-products - Detergents Ammonia Sulfur And Derivatives

PFRSee Plug Flow Reactor.

pHpH is a convenient measure of the acid-base character of a solution, usually defined by

pH = -logc(H+)where c(H+) is the concentration of hydrogen ions in moles per liter. The more

precise definition is in terms af activity rather than concentration.A solution of pH 0 to 7 is acid, pH of 7 is neutral, pH over 7 to 14 is alkaline.

OR

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Measures the acidity of a solution. It is the negative log of the concentration of the hydrogen ions in a substance.

ORIt is the measure of the acidity of a solution; it is the negative log of hydrogen positive ion activity (Concentration)

OR

Negative logarithm of hydrogen ion activity;pH = - log (H+)

pH scale indicates the acidity or alkanity of aqueous solutions; it was developed in 1909 by S.P.L. Sorensen, a Danish biochemist. pH value is a number from 1 to 14, which represents a logarithmic scale indicating the concentration of hydrogen ions. These numbers are actually exponents expressing the molar concentration; water molecule dissociate into H+

and OH- and recombine at such a rate that there is at any instant a concentration of 1/10,000,000 mol per liter, ie 1/107 or 10-7. This is the neutrality point of pure water (pH 7), at which the concentrations of H+ & OH- ions are equal. When an acid is added to the water, numbers from 1 to7 are used to indicate the acidity of the solution, i.e. predominance of hydrogen ions (H+), numbers from 7 to14 are used to indicate the alkalinity of the solution, i.e. predominance of hydroxyl ions (OH-). A pH of 1.0 is represented by 0.1N hydrochloric acid, and a pH of 14 is that of 0.1N sodium hydroxide. Since the ionic concentration increases logarithmically, the value on the pH scale differ by a factor of 10; a pH of 5 is ten times as acidic as a pH of 6.

ORAcidity and alkalinity of aqueous solutions are axpressed in terms of pH. This is a measurement of the hydrogen ion concentration of the solution. Mathematically it is expressed as:

The pH scale of 0-14 covers the range from strong acid to strong base. A neutral solution has the same number of hydrogen ions and hydroxyl ions and this corresponds to pH 7. Values higher than pH 7 are alkaline, whereas if they are lower than pH 7 they are acidic.

ORThe conventional standard pH scale established on the basis that an individual ionic activity coefficient can be calculated from the Debye-H¸ckel law for primary buffers.

PhasePhase is a portion of a physical system (solid, liquid, gas) that is homogeneous throughout, has definable boundaries, and can be separated physically from other phases.

ORA part of the system, that is in a single physical state, and also the chemical composition throughout that part is uniform is called a phase. This part of system is separated from the rest by definable boundaries.

ORA homogeneous region of matter.

Phase DiagramPhase diagram is a graphical representation of the equilibrium relationships between phases (such as vapour-liquid, liquid-solid) of a chemical compound, mixture of compounds, or solution.

ORA graphical representation of the relationships between environmental constraints, composition, and regions of phase stability, ordinarily under conditions of equilibrium.

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Phase TransformationA change in the number and/or character of the phases that constitute the microstructure of an alloy.

PhenolsPhenols are compounds having one or more hydroxy groups attached to benzene or other arene ring.

ORAn aromatic benzene ring with a hydroxyl substituted for one hydrogen.

ORAn organic substance in which a hydroxyl group is attached directly to a benzene ring. An example is vanillin.

PhenylA benzene ring named as a constituent group, C6H5-.

PhononA single quantum of vibrational or elastic energy.

PhosphorylationThe synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP).

PhotoautotrophicOrganisms which utilize inorganic carbon dioxide for protoplasm synthesis and light for an energy source. See autotrophic and chemoautotrophic.

Photochemical PollutantsChemicals which react photochemically (in the presence of sunlight) to destroy ozone in the stratosphere.

Photochemical ReactionA chemical reaction can be enhanced when induced by light, just as some are speeded up by catalysts. Chlorine is one of a number of substances that undergo photochemical reactions. In sunlight, chlorine will react with carbon monoxide to produce the poisonous gas phosgene:

A large number of organic reactions are carried out by irradiating with ultraviolet light.

Photoelectric EffectPhotoelectric effect is the complete absorption of a photon by a solid with the emission of an electron. The energy of a photon (hν) is

hυ = Ei + (mv2 / 2)OR

It is the emission of electrons from metal when the metal is struck by light.OR

Collision process between an x-ray or gamma rays and a bound atomic electron where the photon disappears, the bound electron is ejected, and the incident energy is shared between the ejected electron and the remaining atom. The photon energy must be greater than the atomic binding energy. The probability for the photoelectric effect is approximately proportional to Z5 of the absorber and falls of by about E(gamma)3.5.

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PhotonPhoton is an elementary particle of zero mass and spin 1/2. The photon is involved in electromagnetic interactions and is the quantum of electromagnetic radiation. The photon may also be regarded as a unit of energy equal to

E = h∙νwhere h is Planck constant and ν is the frequency of the radiation.

ORMassless packet of energy, which behaves like both a wave and a particle.

ORA quantum unit of electromagnetic energy.

ORAll matter absorbs and emits electromagnetic radiation in discrete small quantities called photons. The energy of a photon (E) varies withthe frequency of the radiation according to:

- where h is a constant known as Planck's constant.

PiezoelectricA dielectric material in which polarization is induced by the application of external forces.

pKpK is the negative logarithm (base 10) of an equilibrium constant K.

PhotophosphorylationThe synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP) using solar energy.

PhototrophOrganisms which obtain energy from light using photooxidation.

PhthalatePhthalates, or phthalate esters are manufactured from methanol and are used as plasticisers to soften the plastic. They are also used in other non-PVC applications like paints, rubber products, adhesives and some cosmetics.

Physical PropertiesA property that can be measured without changing the chemical composition of a substance. Eg. color, density, hardness, ductility, malleability, solubility, heat conduction, electrical properties, melting and boiling point.

PI (π) BondsA type of covalent bond in which the electron density is concentrated around the line bonding the atoms.

PlanckPlanck contributed to the understanding of the electromagnetic spectrum by realizing that the relationship between the change in energy and frequency is quantized according to the equation delta E=hv where h is Planck's constant.

Planck ConstantPlanck constant (h) is a constant that when multipled by the frequency of radiation gives the quantity of energy contained in one quantum.

E = hνEqual to 6.6260755(40)∙10-34 J s. It is named after Max Planck (1858-1947).

OR

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A universal constant that has a value of 6.63 x 10-34 J.

PlasmaPlasma is a highly ionized gas in which the charge of the electrons is balanced by the charge of the positive ions, so that the system as a whole is electrically neutral. Temperatures of 10 000 °C to 15 000 °C can be reached.

PlasticA solid material in the primary ingredient of which is an organic polymer of high molecular wight.

Plastic DeformationDeformation that is permanent or nonrecoverable after release of the applied load.

PlasticizerA low molecular weight polymer additive that enhances flexibility and workability and reduces stiffness and brittleness.

Plug Flow ReactorThis may be thought of as a long pipe to which the reactants flow in, and the products flow out. In an ideal PFR, the components will be distributed axially, but will have uniform radial distribution.

pOHMeasures the basicity of a solution. It is the negative log of the concentration of the hydroxide ions.

Point DefectA crystalline defect associated with one or, at most, several atomic sites.

Poisson’s RatioFor elastic deformation, the negative ratio of lateral and axial strains that result from an applied axial stress.

ORThe ratio between the strain of expansion in the direction of force and the strain of contraction perpendicular to that force v = -Et/E1.

Polar MoleculesMolecule with a partial charge.

ORA molecule in which there exists a permanent electric dipole moment by virtue of the asymmetrical distribution of positively and negatively charged regions.

Polarization (Electronic)For an atom, the displacement of the center of the negatively charged electron cloud relative to the positive nucleus, which is induced by an electric field.

Polarization (ionic)Polarization as a result of the displacement of anions and cations in opposite directions.

Polarization (Orientation)Polarization resulting from the alignment (by rotation) of permanent electric dipole moments with an applied electric field.

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PollutionAny man made condition which adversely affects the quality of the environment.

PolycrystallineReferring to crystalline materials that are composed of more than one crystal or grain.

PolymerPolymer is a substance composed of molecules of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass (monomers). In most cases the number of monomers is quite large and often is not precisely known. A single molecule of a polymer is called a macromolecule.

ORWhen individual molecules (monomers) link up in a chain-like fashion, they form a polymer. The chemical reaction that forms a polymer is called polymerization.

ORA solid, nonmetallic (normally organic) compound of high molecular weight the structure of which is composed of small repeat (or mer) units.

ORA polymer is a long chain molecule or a complex 3-dimensional lattice produced by the reaction of simple compounds with each other. There are two types of poymerisation. The first, where compounds open a double bond and link together via the radicals formed is called addition polymerisation. eg. the poylmerisation of propylene to polypropylene:

The other main type of polymerisation is condensation polymerisation, where as with condensation reactions, a simple molecule is eliminated during the formation of the polymer, eg. the reaction between adipic acid and hexamethylenediamine to produce nylon:

PolymerizationIn case of petroleum industries, it is defined as the combination of two or more olefinic molecules to yield larger molecules. The operation is of two types :

1) Thermal Polymerization2) Catalytic Polymerization

PolymorphismThe ability of a solid material to exist in more than one form or crystal structure.

PolypeptidesPolypeptides are peptides containing ten or more amino acid residues. The properties of a polypeptide are determined by the type and sequence of its constituent amino acids.

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PolysaccharidesPolysaccharides are compounds consisting of a large number of monosaccharides linked together by glycosidic bonds. Some important examples are starch, glycogen, and cellulose.

PositronPositron is the antiparticle of the electron. It has the same mass and spin as an electron, and an equal but opposite charge.

ORPositron are electrons with a +1 charge. They are found in cosmic rays and in nuclear reactions. They are antimatter. When they meet an electron there is complete annihilation to give pure energy in the form of gamma rays. This is total matter and energy conversion by

E = mc2.

Positron AnnihilationPositron decay in matter by annihilation with an electron. Usually and "atom" of positronium (e+e-) forms which annihilates to produce two 511-keV photons. Occasionally, the positron will annihilate in flight to produce on or more photons sharing the total rest mass and kinetic energy of the positron and electron.Potable WaterWater that has does not contain harmful or objectionable impurities and is aesthetically pleasing to drink.

Potential EnergyThe energy an object has because of its composition or position.

OREnergy related to the position or height above a place to which fluid could possibly flow.

POTW See Publicly Owned Treatment Works

Pour PointThe lowest temperature at which lube oil will flow by gravityfrom a specified container under standard conditions. Since this point is largely dependent on the wax content of the oil, agents called pour point depressants are added to reduce the melting point of the wax. Acrylic acid, esters and alkylated naphthalenes have been used for this purpose.

ORPour point is the lowest temperature at which oil flows when chilled under specified test conditions. It is important if the system is regularly exposed to low ambient temperatures, but relatively insignificant if the system is to be used inside a heated plant. Pour point of the oil should be about 20°F below the lowest expected temperature.

PPMSee Parts Per Million

PrecipitationThe falling to earth of condensed water vapour in the form of rain, snow, sleet or hail.

Precipitation HardeningHardening and strengthening of a metal alloy by extremely small and uniformly dispersed particles that precipitate from a supersaturated solid solution.

PrecisionIt gives consistent results. (Something can be precisely inaccurate.)

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PrepregContinuous fiber reinforcement pre-impregnated with a polymer resin which is then partially cured.

PressurePressure (p) is the force acting normally on unit area of a surface. It is measured in pascals in Si units (Pa)

p = F/AOR

Force per unit area.

Priary BondInteratomic bonds that are relatively strong and for which bonding energies are relatively large.

Primary StandardsRequired drinking water quality standards related directly to human health. These standards are required and enforceable by the U.S. EPA. See secondary standards.

ORAqueous pH buffer solutions established by the National Bureau of Standards within the 2.5 to 11.5 pH range of ionic strength less than 0.1 and which provide stable liquid junction potential and uniformity of electrode sensitivity.

Primary treatmentTreatment which includes all operation prior to and including primary treatment, e.g., bar screening, grit removal, comminution, and primary sedimentation.

Principal Quantum NumberIt gives the energy of the orbital. This is determined by the distance of the electron from the nucleus.

ORThe number related to the amount of energy an electron has and therefore describing which shell the electron is in.

Procaryotic OrganismsOrganisms which do not have a cellular membrane.

ProducersAutotrophic organisms which produce protoplasm using inorganic carbon and energy from the sun.

ProductThe compounds that are formed when a reaction goes to completion.

ProportionAn equality between two ratios.

Proportional LimitThe point on a stress-strain curve at which the straight line proportionality between stress and strain ceases.

ProteinA molecule comprised of long chains of amino acid molecules. Proteins, which include enzymes, are polypeptides.

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ProtonProton is a stable elementary particle of unit positive charge and spin 1/2. Protons and neutrons, which are collectively called nucleons, are the constituents of the nucleus.

ORIt is a basic particle with a charge of +1 and a mass of 1g/mol (amu).

ORParticle found in a nucleus with a positive charge. Number of these gives atomic number.

OROne of the three fundamental particles in atoms. Protons carry a large positive charge, is of similar mass as the neutron but is 1836 times as heavy as an electron.

OROne of the basic particles which makes up an atom. The proton is found in the nucleus and has a positive electrical charge equivalent to the negative charge of an electron and a mass similar to that of a neutron. A proton is a hydrogen nucleus.

Proton DecayNuclear decay by emission of a proton. 

Proton-Proton ChainIn the Sun and other less massive stars, this chain is the primary source of heat and radiation. The proton-proton chain converts hydrogen into helium releasing energy in the form of particles and gamma-rays. Hydrogen is converted into helium in a chain of reactions. The first reaction takes an average of 1 billion years to occur while the others are much shorter. One step is only 1 second long. In the Sun, there are so many hydrogen nuclei that the 1 billion year waiting period does not stop it from producing tremendous radiation.

Proton Separation EnergyThe energy required to remove a proton from a nucleus.

PSIPounds of pressure per square inch.

PSIaPounds/force per square inch absolute.

PSIgPound per square inch gage. Pressure referenced to ambient air pressure.

Publicly Owned Treatment WorksAny municipally owned wastewater treatment facility.

PumpA pump is a device that raises or transfers fluids. Pumps are selected for processes not only to raise and transfer fluids, but also to meet some other criteria. This other criteria may be constant flowrate or constant pressure.

There are two main categories of pumps and they are Dynamic pumps and Positive Displacement pumps. These two categories also have many subcategories of pumps. Positive Displacement Pump - Positive-displacement pumps is one category of pumps.

Types of positive-displacement pumps are Reciprocating, Metering, and Rotary pumps. Positive-displacement pumps operate by forcing a fixed volume of fluid from the inlet pressure section of the pump into the discharge zone of the pump. These pumps generally tend to be larger than equal-capacity dynamic pumps. Positive-displacement pumps frequently are used in hydraulic systems at pressures ranging up to 5000 psi.

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Dynamic Pumps - Dynamic pumps are one category of pumps under which there are several classes, two of which are: Centrifugal and Axial. These pumps operate by developing a high liquid velocity and converting the velocity to pressure in a diffusing flow passage. Dynamic pumps usually have lower efficiencies than positive displacement pumps, but also have lower maintenance requirements. Dynamic pumps are also able to operate at fairly high speeds and high fluid flow rates.

Pumps are used for a variety applications. Here is a list of a few applications:

Drainage - Used to control the level of water in a protected area. Sewage - Used in the collection and treatment of sewage. Irrigation - Used to make dry lands agriculturally productive. Chemical Industry - Used to transport fluids to and from various sites in the chemical

plant. Petroleum Industry - Used in every phase of petroleum production, transportation, and

refining. Medical Field - Used to pump fluids in and out of the body. Steel Mills - Used to transport cooling water.

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QQIt is the rate of heat flow (transfer) and is given by:

Conduction Q = -k.A(dT/dn)where

Q = Rate of Heat Flowk = The proportionality constant (thermal conductivity)A = Area of cross-sectionT = Temperaturen = Distance measured normal to the surface (in the direction of heat flow)q = Heat Flux (i.e. Rate of heat flow per unit area)

Convection Q = k.A.ΔT / x = h.A.ΔT = U.A.ΔTlm = m.Cp.ΔT

whereQ = Rate of Heat Flowx = Effective Thickness of Filmh = Film Heat Transfer Coefficient (Film Coefficient)U = Overall Heat Transfer CoefficientA = Heat Transfer AreaΔT = Difference Between Temperature of Hot and Cold Fluid (TH – TC)ΔTlm = Log Mean Temperature Differencem = Mass Flow Rate of FluidCp = Specific Heat

Radiation Q = e.σ.A(T14 – T2

4)

whereQ = Rate of Heat Flowe = Emissivityσ = Stefan-Boltzmann constant = 5.67 x 10-8 W/(m2.K4)A = Heat Transfer Surface = π.D.LT1 = Higher TemperatureT2 = Lower Temperature

qSee Heat Flux and Volumetric Flow Rate

Q-ValueThe energy available for decay. This energy is released by the nucleus mainly as gammas, betas, neutrinos, and/or alpha particles.

Qualitative AnalysisQualitative analysis involves determining the nature of a pure unknown compound or the compounds present in a mixture.

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Quality AssuranceQA is a global term used to incorporate the quality policy, quality management and quality control functions, which combine to assure the client that the product will be consistently manufactured to the required condition. Its aim is to achieve and assure quality through the adoption of a cost effective quality control system and through external inspections and audits.

ORIn developing products and services, quality assurance is any systematic process of checking to see whether a product or service being developed is meeting specified requirements.

ORIt covers all activities from design, development, production, installation, servicing and documentation. It introduced the sayings "fit for purpose" and "do it right the first time". It includes the regulation of the quality of raw materials, assemblies, products and components; services related to production; and management, production, and inspection processes.

ORSteps taken to make sure that a company's products or services are of sufficiently high quality.

Quality ControlSee Quality Assurance

QuantumQuantum is the smallest quantity of energy that can be emitted (or absorbed) in the form of electromagnetic radiation. Energy of a quantum (E) is equal to

E = h∙νwhere h is Planck constant and ν is the frequency of the radiation.

ORSomething which comes in discrete units. Eg, money is quantized (divided into units); it comes in quanta (divisions) of one cent.

Quantum NumbersIt describe the distance, shape, and orientation of the electronic orbitals.

ORSet of numbers used to describe an electron's position.

QuasicrystalQuasicrystal is a solid having conventional crystalline properties but whose lattice does not display translational periodicity.

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RRSee Universal Gas Constant

RacemateRacemate is a mixture of equal quantities of the d- and l-forms of an optically active compound. A racemic mixture is not optically active.

RadicalA radical is a reaction intermediate where a bond is broken and the two parts of the molecule exist carrying a single unshared electron. The radicals are normally destroyed quickly by recombination or they break in another radical and a stable molecule.

Radient EnergyEnergy which is transmitted away from its source. eg, energy that is emitted when electrons transition down from one level to another.

RadiationEnergy in the form of photons.

RadioactiveSubstance containing an element which decays.

Raman EffectRaman effect is a type of scattering of electromagnetic radiation in which light suffers a change in frequency and a change in phase as it passes through a material medium. Is named according to the Indian physicist C. V. Raman (1889-1970). The intensity of Raman scattering is about one-thousandth of that in Rayleigh scattering in liquids.

Random CopolymerA polymer in which two different mer units are randomly distributed along the molecular chain.

Rankine ScaleRankine cycle is a thermodynamic cycle which can be used to calculate the ideal performance of a heat engine that uses a condensable vapour as the working fluid.

ORAn absolute temperature scale based upon the Fahrenheit scale with 180° between the ice point and boiling point of water. 459.67°R = 0°F.

Raoult’s LawIt states that the equilibrium pressure of a component is equal to the product of vapour pressure and the mole fraction of that component in liquid phase, i.e.

pA = pAo xA

where xA is the mole fraction of component A and pAo the vapour pressure of

the pure substance A.also,

pA = yA.Pwhere yA is the mole fractio of that component in gas phase.

ORRaoult's law is the expression for the vapour pressure pA of component A in an ideal solution, viz.,

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pA = pAo xA

where xA is the mole fraction of component A and pAo the vapour pressure of the pure

substance A.

Rare Earth ElementsRare earth elements are the elements Sc, Y, and the lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). These elements got their name from the fact that chemists first isolated them in their oxide forms. These oxides somewhat resemble calcium, magnesium and aluminum oxides, sometimes called common earths.

RatioThe relative size of two quantities expressed as the quotient of one divided by the other; the ratio of a to b is written as a:b or a/b.

Rayleigh ScatteringRayleigh scattering is the scattering of light by particles which are much smaller than the wavelength of the light.

RDFSee Refuse Derived Fuel

ReactantsSubstances initially present in a chemical reaction.

Reactive WasteA waste which; 1) reacts violently with water, 2) forms potentially explosive mixtures with water, 3) is normally unstable, 4) contains cyanide or sulfide in sufficient quantity to evolve toxic fumes at high or low pH, 5) is capable of exploding if heated under pressure, or 6) is an explosive compound listed in Department of Transportation (DoT) regulations. One of EPA's four hazardous waste properties.

ReaerationThe dissolving of molecular oxygen from the atmosphere into the water.

Receiving WaterA water which receives wastewater (treated or otherwise) discharges.

Receiving Water Quality StandardsStandards which require a discharger to maintain a certain quality level in the receiving water.

RecrystallizationThe formation of a new set of strain-free grains within a previously cold-worked material; normally an annealing heat treatment is necessary.

RecyclingThe recovery and reuse of a product which would otherwise be thrown away.

ReductionA reaction in which a substance gains at least one electron.

ORThe addition of hydrogen and the removal of oxygen - the oppposite to oxidation, but is now generalised to the inclusion of electrons to a substance by any means.

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ReflectionDeflection of a light beam at the interface between two media.

ReflectivityIt is the fraction of incident radiations, that is reflected by the body. It may be denoted by letter ‘r’

ReformingReforming means rearrangement of molecules without much affecting the average molecular weight of feed. In refineries, reforming is generally carried out to produce high quality (octane number) gasoline by heating with or without the catalyst. The process of reforming can also be carried out in two ways, classified as :

1) Thermal Reforming2) Catalytic Reforming

RefractionBending of a light beam upon passing from one medium into another.

Refractive IndexThe ratio of the velocity of light in a vacuum to the velocity of light in some medium.

ORFor a non-absorbing medium, index of refraction (n) is the ratio of the velocity of electromagnetic radiation in vacuo to the phase velocity of radiation of a specified frequency in the medium.

RefractoryA metal or ceramic that may be exposed to extremely high temperatures without deteriorating rapidly or without melting.

RefuseAll forms of solid waste.

Refuse derived fuelA fuel derived from the combustible portion of municipal solid waste. The fuel is often processed into small briquettes, similar in size to charcoal.

RegelationIt is the process of melting ice by pressure. Inasmuch as water expands upon freezing, pressure will reverse the process, forcing water to melt. Then when the pressure is released, the water re-freezes (re-gells).

Relative Atomic MassRelative atomic mass (Ar) is the ratio of the average mass per atom of the naturally occurring form of an element to 1/12 of the mass of nuclide 12C. The term atomic weight is synonymous with relative atomic mass.

Relative DensityRelative density is the ratio of the density of a substance to the density of some reference substance. For liquids or solids it is the ratio of the density (usualy at 20 °C) to the density of water at 4 °C. This quantity was formerly called specific gravity.

Relative HumidityRelative humidity is the ratio of the partial pressure of water vapour in air to the saturation vapour pressure of water at the same temperature, expressed as a percentage.

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Relative Molecular MassRelative molecular mass (Mr) is the ratio of the average mass per molecule or specified entity of a substance to 1/12 of the mass of nuclide 12C. Also called molecular weight. It is equal to the sum of the relative atomic masses of all the atoms that comprise a molecule. For example

Mr(H2SO4) = 2×Ar(H) + Ar(S) + 4×Ar(O)= 2×1.0079 + 32.066 + 4×15.999= 2.0158 + 32.066 + 63.996= 98.078

RemRem (rem) (roentgen equivalent man) is a non-SI unit of dose equivalent employed in radioprotection (rem = 10-2 Sv).

ResistanceResistance (R) is electric potential difference divided by current when there is no electromotive force in the conductor. This definition applies to direct current. More generally, resistance is defined as the real part of impedance.

ResistivityThe reciprocal of electrical conductivity, and a measure of a material's resistance to the passage of electric current.

RespirationEnergy production in which oxygen is the terminal electron acceptor, i.e. oxidation to produce energy where oxygen is the oxidizing agent. See fermentation.

Reversible ReactionA reaction in which the reactant(s) proceed to product(s), but the products react at an appreciable rate to reform reactant(s).

Reynolds NumberReynolds number (Re) is a dimensionless quantity used in fluid mechanics, defined by

Re = Dvρ/μwhere ρ is density, v is velocity, D is the inside diameter of pipe, and μ is viscosity.

ORThis is a number which characterises flow. If the Reynold's number is low (under approximately 1800) then the flow is said to be laminar. This may be thought of as the fluid flowing in layers. If the Reynold's number is high (over approximately 2300) then the flow is said to be turbulent. Turbulent flow is considered to be well mixed.

ORThe ratio of inertial and viscous forces in a fluid defined by the formula

Re = Dvρ/μwhere ρ is density of fluid, v is velocity, D is the inside diameter of pipe, and μ is viscosity in centipoise.

RheologyRheology is the study of the deformation and flow of materials. Has important bearing on the behavior of viscous liquids in plastic molding.

Ribo-nucleic AcidRibonucleic acids (RNA) is naturally occurring polyribonucleotides that is concerned with protein synthesis. Four types are recognized: messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA), and viral RNA.

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RMSSee Root Mean Square

RNASee Ribo-Nucleic Acid

Root Mean SquareSquare root of the mean of the square of the signal taken during one full cycle.

RunoffThe water that flows overland to lakes or streams during and shortly after a precipitation event.

RuptureFailure that is accompanied by significant plastic deformation.

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SSalinitySalinity (S) is a parameter used in oceanography to describe the concentration of dissolved salts in seawater. The salinity of normal seawater is 35 parts salt per 1000 parts water.

SaltSalt is an ionic compound formed by the reaction of an acid and a base. The reaction of sodium hidroxide to hydrochloric acid give sodium chloride

NaOH + HCl ⇌ NaCl + H2OOR

Ionic compounds that can be formed by replacing one or more of the hydrogen ions of an acid with another positive ion.

ORThe ionic product of a reaction between an acid and a base. Water is also formed

Salt BridgeSalt bridge is a permeable material soaked in a salt solution that allows ions to be transferred from one container to another. The salt solution remains unchanged during this transfer.

Salt EffectThe effect on the activity coefficient due to salts in the solution.

Saltwater IntrusionThe gradual replacement of freshwater by saltwater in coastal areas where excessive pumping of groundwater occurs.

SAMAScientific Apparatus Makers Association. An association that has issued standards covering platinum, nickel, and copper resistance elements (RTDs).

Saturated CompoundAn organic compound that does not comprise of carbon-carbon multiple bonds. Examples include ethane and propane.

Saturated SolutionSaturated solution is a solution that holds the maximum possible amount of dissolved material. When saturated, the rate of dissolving solid and that of recrystallisation solid are the same, and a condition of equilibrium is reached. The amount of material in solution varies with the temperature; cold solutions can hold less dissolved solid material than hot solutions. Gases are more soluble in cold liquids than in hot liquids.

Schiff BaseSchiff base is a class of compounds derived by chemical reaction (condesation) of aldehydes or ketones with aromatic amines, for example

RNH2 + R'CHO ⇌ RN:CHR' + H2OThey are named after the German chemist Hugo Schiff (1834-1915).

Second

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Second (s) is the SI base unit of time. The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels (F = 4, mF = 0 to F = 3, mF = 0) of the ground state of the caesium 133 atom.

Second Quantum NumberDescribes sublevels. The sublevels are called, s, p, d, f. s orbitals are spherical in shape. p orbitals are dumbbell shaped.

Secondary StandardsRecommended drinking water quality standards which relate to aesthetics and/or health. These standards are recommended, not required. See primary standards.

ORpH buffer solutions which do not meet the requirements of primary standard solutions but provide coverage of the pH range not covered by primary standards. Used when the pH value of the primary standard is not close to the sample pH value.

Secondary TreatmentIn wastewater treatment, the conversion of the suspended, colloidal and dissolved organics remaining after primary treatment into a microbial mass with is then removed in a second sedimentation process. Secondary treatment included both the biological process and the associated sedimentation process.

Secured LandfillA landfill which has containment measures such as liners and a leachate collection system so that materials placed in the landfill will not migrate into the surrounding soil, air and water.

SedimentationThe gravity settling, and thus removal, of materials more dense than the suspending fluid.

Sedimentation BasinSee clarifier.

SelectivityIt is the the effectiveness of solvent for separating a solution of A and B into its components. Numerically, it is the ratio of the concentration ratios of solute to feed solvent in the extract phase (solvent rich product of operation) to that in raffinate phase (the residual solution, from which solute is removed).

If C is solvent, feed (solution) contains A (feed solvent) and B (feed solute):

Selectivity = [wt. fraction of B / wt. fraction of A] Extract

[wt. fraction of B / wt. fraction of A] Raffinate

SelenidesSelenides are compounds having the structure RSeR (R not equal to H). They are thus selenium analogues of ethers. Also used for metal salts of H2Se.

Semi-metalSee Metalloid

SemiconductorSemiconductor is a material in which the highest occupied energy band (valence band) is completely filled with electrons at T = 0 K, and the energy gap to the next highest band

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(conduction band) ranges from 0 to 4 or 5 eV. With increasing temperature electrons are excited into the conduction band, leading to an increase in the electrical conductivity.

Sensible HeatSee Specific Heat. SensitivityThe minimum change in input signal to which an instrument can respond.

Shear StressWhere normal stress is perpendicular to the designated plane, shear stress is parallel to the plane.

Shearing StrainA measure of angular distortion also directly measurable, but not as easily as axial strain. ShellsWhere the electrons generally stay. There are 4 types of electron shells: s, p, d and f shells.

Shock LoadInfluent wastewater entering the plant which has an unusually high organic content and/or high flow rate.

SI UnitsStands for Systeme International d'Unites, a international system which established a uniform set of measurement units. See also International System of Units

ORSystem Internationale. The name given to the standard metric system of units.

ORInternational System of Units (SI) is the unit system adopted by the General Conference on Weights and Measures in 1960 and recommended for use in all scientific and technical fields. It consists of seven base units (meter, kilogram, second, ampere, kelvin, mole, candela), plus derived units and prefixes.

SiemensSiemens (S) is the SI derived unit of of electrical conductance of a conductor in which a current of one ampere is produced by an electrical potential difference of one volt (S = A∙V -1

= Ω-1). The unit is named after the German scientist Ernst Werner von Siemens (1816-1892).

SieyertSievert (Sv) is the SI derived unit of dose equivalent when the absorbed dose of ionizing radiation multiplied by the stipulated dimensionless factors is 1 J/kg. It is named after the Swedish physicst Rolf Sievert (1896-1966).

Sigma BondA type of covalent bond in which most of the electrons are located in between the nuclei

Significant DigitThose that can be accurately measured. An answer can have no more significant digits than the least number of them in the data.

Significant FigureMeasurements are not infinitely accurate: we must estimate measurement uncertainty. The number of significant figures is all of the certain digits plus the first uncertain digit.Rules for significant figures:1. Disregard all initial zeros.

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2. Disregard all final zeros unless they follow a decimal point.3. All remaining digits including zeros between nonzero digits are significant.

0.0023 have two significant figures

0.109 have three significant figures

2.00 have three significant figures

70 have one significant figure

In adition and subtraction, the number of significant figures in the answer depends on the original number in the calculation that has the fewest digits to the right of the decimal point.In multiplication and division, the number of significant figures in a calculated result is determined by the original measurement that has the fewest number of significant digits.In a logarithm of a number, keep as many digits to the right of the decimal point as there are significant figures in the original number.In an antilogarithm of a number, keep as many digits as there are digits to the right of the decimal point in the original number.

SilanesSilanes are saturated silicon hydrides, analogues of the alkanes (compounds of the general formula SinH2n+2).

SiliconesSilicones are polymeric or oligomeric siloxanes, usually considered unbranched, of general formula [-OSiR2-]n (R not equal to H).

SiloxanesSiloxanes are saturated silicon-oxygen hydrides with unbranched or branched chains of alternating silicon and oxygen atoms (-Si-O-Si-).

Site RemediationThe process of cleaning up a hazardous waste disposal site that has either been abandoned or that those responsible either refuse to cleanup or are financially unable to cleanup.

SitingObtaining government (federal, state, and local) permission to construct an environmental processing, treatment, or disposal facility at a given site.

SludgeA mixture of solid waste material and water. Sludges result from the concentration of contaminants in water and wastewater treatment processes. Typical wastewater sludges contain from 0.5 to 10 percent solid matter. Typical water treatment sludges contain 8 to 10 percent solids.

SmogSmog is a mixture of smoke and fog. The term is used to describe city fogs in which there is a large proportion of particulate matter (tiny pieces of carbon from exhausts) and also a high concentration of sulphur and nitrogen gases.

Single BondWhen an electron pair is shared by two different elements.

Sodium HydroxideSodium hydroxide (NaOH) is a white, translucent, hygroscopic alkali manufactured by the electrolysis of sodium chloride. Hydrates containing 7, 5, 4 (two forms α & β), 3.5, 3, 2 and 1 molecules of water of crystallization are known. At high temperatures (about 1300°C) the compound decomposes into its elements , and reduction with hydrogen can be detected at

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800°C; metals at 318.4°C in vacuum and boils at 1388°C in vacuum. Sodium hydroxide is one of the most important commercial caustics, used in the manufacture of soaps, detergents, rayon, cellophane, and a large number of other compounds. It is corrosive to tissues in the presence of moisture, and is a strong irritant. Occupational exposure to sodium hydroxide is defined as exposure to airborne concentration of sodium hydroxide at or above one half of the recommended workplace environmental limit. Occupational exposure to sodium hydroxide should be controlled so that no employee is exposed to sodium hydroxide at a concentration greater than 2.0 mg/m3 of air, for any 15 minute period. Also known as caustic soda.

SofteningThe removal of divalent cations by precipitation or ion exchange.

SolSols are dispersions of small solid particles in a liquid. The particles may be macromolecules or may be clusters of small molecules. Lyophobic sols are those in which there is no affinity between the dispersed phase and the liquid (e.g. silver chloride dispersed in water). Lyophobic sols are inherently unstable, in time the particles aggregate, and form a precipitate. Lyiophilic sols, on the other hand, are more like true solutions in which the solute molecules are large and have an affinity for the solvent (e.g. starch in water). Association colloids are systems in which the dispersed phase consists of clusters of molecules that have lyophobic and lyophilic parts (e.g. soap in water).

SolidificationSee chemical fixation.

Solids FluxSee flux.

SolubilitySolubility is the maximum amount of solute that dissolves in a given quantity of solvent at a specific temperature. Generally, for a solid in a liquid, solubility increases with temperature; for a gas, solubility decreases. Common measures of solubility include the mass of solute per unit mass of solution (mass fraction), mole fraction of solute, molality, molarity, and others.

Solubility Product ConstantSolubility product constant (Ksp) (or the solubility product) is the product of the molar concentrations of the constituent ions, each raised to the power of its stoichiometric coefficient in the equilibrium equation. For instance, if a compound AaBb is in equilibrium with its solution

AaBb(s) ⇌ aA+ + bBthe solubility product is given by

Ksp(AaBb) = [A+]a∙[B-]b

SoluteWhat is dissolved in a solution eg, the salt in saltwater.

SolutionUniformly dispersed mixtureof the solvent and the solute. The solvent can be water or any other fluid and solute is the dissolved substance.

ORMixture of a solid and a liquid where the solid never settles out, eg saltwater.

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SolventA solvent is a liquid that has the ability to dissolve, suspend or extract other materials, without chemical change to the material or solvent. Solvents make it possible to process, apply, clean or separate materials. Water is an inorganic solvent. Organic solvents include hydrocarbon solvents, oxygenated solvents and chlorinated solvents.

ORLiquid in which something is dissolved, eg the water in saltwater.

ORA solvent is a substance capable of reataining its physical state whilst forming a homogenous mixture with one or more substances. Some common solvents are listed below:

Source ReductionThe elimination or reduction of the waste at the source by modification of the actual process which produces the waste.

SpeciesIn chemistry, an ion or molecule in solution.

Specific GravitySpecific gravity is ratio of the density of a material to that density of a water. Since one must specify the temperature of both the sample and the water to have a precisely defined quantity, the use of this term is now discouraged.

ORThe ratio of mass of any material to the mass of the same volume of pure water at 4°C.

Specific HeatSpecific heat is the quantity of heat required to raise the temperature of one gram of a substance by one degree Celsius.

ORThe amount of heat it takes for a substance to be raised one degree C.

ORThe ratio of thermal energy required to raise the temperature of a body 1° to the thermal energy required to raise an equal mass of water 1°.

ORThe quantity of heat required to change the temperature of one unit weight of a material by one degree.

ORThe heat energy stored in a substance as a result of an increase in its temperature.

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Specific QuantitySpecific quantity is often convenient to express an extensive quantity (e.g., volume, enthalpy, heat capacity, etc.) as the actual value divided by mass. The resulting quantity is called specific volume, specific enthalpy, etc.

Specific WeightSpecific Weight is defined as weight per unit volume.

Spontaneous FissionNuclear decay by splitting the nucleus into two parts (fission fragments), neutrons, and gamma rays. 

Spontaneous ReactionA reaction that will proceed without any outside energy.

StabilizationSee chemical fixation.

StabilizerA stabilizer is a substance added to another substance to prevent an alteration of its physical state.

Stagnation PressureThe sum of the static and dynamic pressure.

Standard Electrode PotentialStandard electrode potential (E°) (standard reduction potentialis) are defined by measuring the potential relative to a standard hydrogen electrode using 1 mol solution at 25 °C. The convention is to designate the cell so that the oxidized form is written first. For example,

Pt(s)|H2(g)H+(aq)|Zn2+(aq)|Zn(s)The e.m.f. of this cell is -0.76 V and the standard electrode potential of the Zn2+|Zn half cell is -0.76 V.

Standard Hydrogen Electrode Standard hydrogen electrode is a system in which hydrogen ion and gaseous hydrogen are present in their standard states. The convention is to designate the cell so that the standard hydrogen electrode is written first.

H2(g) ⇌ 2H+(aq) + 2e-

The electrode is used as a reference (of zero) for the values of other standard electrode potentials.

Standard Mean Ocean WaterStandard mean ocean water (SMOW) is a standard sample of pure water of accurately known isotopic composition which is maintained by the International Atomic Energy Agency. It is used for precise calibration of density and isotopic composition measurements.

Standard Temperature And PressureSee STP

StandardsStandards are materials containing a known concentration of an analyte. They provide a reference to determine unknown concentrations or to calibrate analytical instruments.

The accuracy of an analytical measurement is how close a result comes to the true value. Determining the accuracy of a measurement usually requires calibration of the

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analytical method with a known standard. This is often done with standards of several concentrations to make a calibration or working curve.

A primary standard is a reagent that is extremely pure, stable, has no waters of hydration, and has a high molecular weight.

A secondary standard is a standard that is prepared in the laboratory for a specific analysis. It is usually standardized against a primary standard.

State PropertyA state property is a quantity that is independent of how the substance was prepared. Examples of state properties are altitude, pressure, volume, temperature and internal energy.

States of MatterSolid, liquid, gas and plasma. Plasma is a "soup" of diassociated nuclei and electrons, normally found only in stellar objects.

Steady FlowA flow rate in the measuring section of a flow line that does not vary significantly with time.

Steam DistillationSteam distillation is especially adopted in cases where substances involved cannot withstand temperature of distillation and decompose (i.e. for heat sensitive materials). Substances of this kind can be separated by reducing the partial pressure of the volatile component. This can be done by making use of inert vapour, that decreases the temperature of distillation. The inert vapour should be practically immiscible with components to be distilled. Steam is generally used for this purpose and operation is called as steam distillation.

In this type of distillation, steam is directly admitted into the liquid in the still. The mixed vapour containing the desired component is taken as overhead, condensed and desired component is separated from water phase by gravity, while non-volatile material remains behind in the still. The necessary condition for employing steam distillation is that the solubility of steam in the liquid must be very low, i.e. product must be practically immiscible with water.

ORA simultaneous distillation of a substance immiscible with water and of water at a temperature such that the combined vapour pressure of the substance and of the water is equal to the external (usually atmospheric) pressure. Volatilization of high boiling substances or of substances, which would decompose at their normal boiling points, is readily affected in this manner. The operation of steam distillation, as normally carried out, consists of distilling a mixture of two immiscible liquids (eg. Of aniline and water) in a current of steam.

Stefan-Boltzmann LawIt states that the total energy emitted by a black body is directly proportional to the fourth power of its absolute temperature, i.e.

Eb is proportional to T4

Or Eb = σ.T4

where T = Temperature in Kσ = Stefan_Boltzmann constant

SterilizationThe destruction or inactivation of all microorganisms. See Disinfection.

StiffnessThe ratio of the force required to create a certain deflection or movement of a part expressed as (Force/deflection) lbs/in or grams/cm.

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Stoichiometric NumberStoichiometric number (ν) is the number appearing before the symbol for each compound in the equation for a chemical reaction. By convention, it is negative for reactants and positive for products.

StoichiometryStoichiometry is the relative proportions in which elements from compounds or in which substances react. Every chemical reaction has its characteristic proportions. For example, when methane unites with oxygen in complete combustion, 1 mol of methane requires 2 mol of oxygen.

CH4 + 2O2 ⇌ CO2 + 2H2OAt the same time, 1 mol of carbon dioxide and 2 mol of water are formed as reaction productions.

Alternatively, 16 g of methane and 64 g of oxygen produce 44 g of carbon dioxide and 36 g of water.

ORThe study of the relationships between amounts of products and reactants.

StorageThe short term retention of water after a precipitation event.

STPStandard temperature (273.15 K) and pressure (101 325 Pa) is the standard conditions used as a basis for calculations involving quantities that vary with temperature and pressure. These conditions are used when comparing the properties of gases.

ORStandard temperature and pressure. This is 0oC and 1 atm.

StrainThe ratio of the change in length to the initial unstressed reference length.

StratosphereStratosphere is the part of the earth's atmosphere extending from the top of the troposphere (typically 10 km to 15 km above the surface) to about 50 km. It is characterized by an increase in temperature with increasing altitude.

ORThe atmosphere from approximately 12 km to 70 km. The temperature of the atmosphere increases in this region.

Stream Based StandardsSee Receiving Water Quality Standards.

StrokeThe distance the piston travels from bottom dead center to top dead center within the cylinder.Strong AcidAn acid that, for practical purposes, ionizes completely under the conditions of interest. Common strong acids are hydrochloric, nitric, and sulfuric. See weak acid.

SublevelOne part of a level, each of which can hold different numbers of electrons.

Substrate Level PhosphorylationThe synthesis of the energy storage compound adenosine triphosphate (ATP) from adenosine diphosphate (ADP) using organic substrates without molecular oxygen.

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Super Heating1. The heating of a liquid above its boiling temperature without the formation of the gaseous phase.2. The heating of the gaseous phase considerably above the boiling-point temperature to improve the thermodynamic efficiency of a system.

SuperconductorSuperconductor is a material that experiences a nearly total loss of electrical resistivity below a critical temperature Tc.

SuperfluidSuperfluid is a fluid with near-zero viscosity and extremely high thermal conductivity. Liquid helium exhibits these properties below 2.186 K (the λ point).

Surface WaterWater which is contained in lakes, rivers, and oceans.

SurfactantSurfactants are products used as detergents, dispersing agents, emulsifiers, wetting agents, foaming or anti-foam agents, and solubilisers. They also constitute the raw material for the formulation of household products such as fabric detergents, shampoos, housecleaning products, as well as industrial auxiliary products for facilitating work in the manufacture of textile, flotation agents for ore, metal working, etc. They are used in other sectors of industry such as food processing, metallurgy, pharmaceuticals and public works.

ORA surface-active agent; one that accumulates at the interface between two liquids and modifies their surface properties. An example would include the sterate ion.

Suspended Growth ReactorA reactor in which the microorganisms are suspended in the wastewater. Examples of suspended growth reactors are activated sludge reactors and anaerobic digesters. See Attached Growth Reactor.

SynergismIt is the act of working together. Two chemicals which are synergistic have a greater effect together than the sum of their individual effects. The effect can be either positive or negative.

SystemAn arbitrarily defined area or volume surrounded by a boundary and possessing specific inputs, outputs, and reactions.

Systeme International d'UnitesSee SI Units

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TTDSSee Total dissolved Solids

Technical CeramicA ceramic that exhibits a high degree of industrial efficiency through carefully designed microstructures and superb dimensional precision.

TeflonA fluorocarbon polymer used for insulation of electrical wires (trademark of DuPont Company).

TemperatureTemperature is measure to the average kinetic energy of its molecules. The SI unit in which thermodynamic temperature is expressed is the kelvin (K).

TEMPCOSee Temperature Coefficient

Temperature CoefficientThe error introduced by a change in temperature. Normally expressed in %/°C or ppm/°C.

TermEach compound or element in a chemical equation.

TeslaTesla (T) is the SI derived unit of magnetic flux density. The tesla is magnetic flux density of a magnetic flux of one weber per square metre (T = Wb/m2). The unit is named after the Croatian scientist Nikola Tesla (1857-1943), equal to V s/m2.

ORAfter Nikola Tesla, a Croation born in what was then part of Austria-Hungary is now is Yugoslavia. He came to the U.S. at the age of 27, became an American citizen, and lived in the U.S. the rest of his life (1856-1943). The tesla is a unit of magnetic flux density, also called magnetic induction.

Theoretical YieldTheoretical yield is the maximum quantity of a product that could be formed in a chemical reaction if all the limiting reactant reacted to form products (distinguished from actual yield).

Thermal ConductivityThermal conductivity (k) is rate of heat flow divided by area and by temperature gradient.

ORThe property of a material to conduct heat in the form of thermal energy.

ORThis is a positive constant, k, that is a property of a substance and is used in the calculation of heat transfer rates for materials. It is the amount of heat that flows through a specified area and thickness of a material over a specified period of time when there is a temperature difference of one degree between the surfaces of the material.

Thermal CrackingThe heavy hydrocarbon molecules are subjected to high temperature and pressure, when the bigger hydrocarbon molecules break down to give smaller molecules of paraffins, olefins

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and some hydrogen. This process can either be carried out either in liquid phase or vapour phase.

Thermal ExpansionAn increase in size due to an increase in temperature expressed in units of an increase in length or increase in size per degree, i.e. inches/inch/degree C.

Thermal GradientThe distribution of a differential temperature through a body or across a surface.

Thermal ReformingIt is carried out in absence of catalyst, and under high temperature, low pressure.

Thermionic EmissionIt is the boiling off of electrons from heated metals. It gives a source of electrons for cathode ray tubes.

ThermoclineThe depth at which an inflection point occurs in a lake temperature profile.

Thermodynamic LawsThermodynamic laws are the foundation of the science of thermodynamics:First law: The internal energy of an isolated system is constant; if energy is supplied to the system in the form of heat dq and work dw, then the change in energy dU = dq + dw.Second law: No process is possible in which the only result is the transfer of heat from a reservoir and its complete conversion to work.Third law: The entropy of a perfect crystal approaches zero as the thermodynamic temperature approaches zero.

ThermodynamicsThermodynamics is the scientific study of the interconversion of heat and other forms of energy.

ORThe study of heat and energy flow in chemical reactions.

ThermosphereThermosphere is the layer of the earth's atmosphere extending from the top of the mesosphere (80 km - 90 km above the surface) to about 500 km. It is characterized by a rapid increase in temperature with increasing altitude up to about 200 km, followed by a leveling off in the 300 km - 500 km region.

ThiolsOrganic compounds which contain the "-SH" functional group. Also called mercaptans.This term not only embraces mercaptans, but also covers thioethers, and thiophenols.

Thomson EffectWhen current flows through a conductor within a thermal gradient, a reversible absorption or evolution of heat will occur in the conductor at the gradient boundaries.

Three Way Safety BulbThe three way safety bulb is used for pipeting. The attachment is placed over the mouth of the pipet. The air (A) valve is used to empty the bulb of air. The suction (S) valve is used to draw liquid into the pipet. The empty (E) valve is used to drain liquid out of a pipet.

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TitrationReacting a solution of unknown concentration with a solution of a known concentration for the purpose of finding out more about the unknown solution.

Titration CurveTitration curve is a graphical representation of the amount of a species present (often hydrogen ion) vs. volume of solution added during a titration.

TonneTonne (t) is an alternative name for megagram (1000 kg).

Total Dissolved SolidsIt is the amount of dissolved matter in the water.

Total SolidsIt is the amount of organic and inorganic matter which is contained in a water.

Total Suspended SolidsIt is the amount of suspended (filterable) matter in a water.

ToxicityA U.S. EPA hazardous waste characteristic defined with a rigorous test procedure, the TCLP (for Toxicity Characteristic Leaching Procedure). In the procedure, a waste is extracted for 24 hours with an acetic acid solution. The acid extract is then analyzed for the presence of any of the contaminants listed in the procedure.

Trace ContaminantsContamination found in trace (very low) levels.

Transition MetalThis group of metals is distinguished from other metals not by their physical properties, but by their electronic structure. Transition metals are elements characterized by a partially filled d subshell. The First Transition Series comprises scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu). The Second and Third Transition Series include the lanthanides and actinides, respectively.

The transition metals are noted for their variability in oxidation state. Thus, manganese has two electrons in its outside shell and five electrons in the next shell down, and exhibits oxidation states of +1, +2, +3, +4, +5, +6, and +7.

They are also characterized by the fact that well into the series, going from left to right, the properties of succeeding metals do not differ greatly from preceding ones.

Transitional FlowFlow between laminar and turbulent flow, usually between a pipe Reynolds number of 2000 and 4000.

TransmissivityIt is the fraction of incident radiations, that is transmitted through the body. It may be denoted by letter ‘τ’

TransmutationThe conversion of one element into another by a process taking place in the nucleus.

TranspirationThe loss of water from plants through leaves and other parts. This loss can be a significant amount of water during very dry periods.

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Trickling FilterAn attached growth biological process in which the microbial film is attached to non-moving rock or plastic media.

Triple PointTriple point is the point in p,T space where the solid, liquid, and gas phases of a substance are in thermodynamic equilibrium.

ORThe temperature and pressure at which solid, liquid, and gas phases of a given substance are all present simultaneously in varying amounts. The triple point of water is .01°C.

Trophic LevelA level in the food chain. The first trophic level consists of the primary producers, autotrophs. The second trophic level is vegetarians which consume autotrophic organisms.

TroposphereTroposphere is the lowest part of the earth's atmosphere, extending to 110 km to 15 km above the surface. It is characterized by a decrease in temperature with increasing altitude. The exact height varies with latitude and season.

ORThe lower atmosphere, from the earth's surface to approximately 12 km. This portion of the earth's atmosphere contains about 95 percent of the atmospheric gases. The temperature gradually declines through this region.

TSSee Total Solids

TSSSee Total Suspended Solids

Turbulent FlowWhen forces due to inertia are more significant than forces due to viscosity. This typically occurs with a Reynolds number in excess of 4000.

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UUltimate Biochemical Oxygen DemandThe total amount of oxygen required to oxidize any organic matter present in a water, i.e. after an extended period, such as 20 or 30 days.

Ultimate disposalThe process of returning residuals back to the environment in a form which will have the minimal or reduced negative environmental impacts.

UndershootThe difference in temperature between the temperature a process goes to, below the set point, after the cooling cycle is turned off and the set point temperature.

Unified Atomic Mass UnitUnified atomic mass unit (u or mu) is a unit of mass used in atomic, molecular, and nuclear science, defined as the mass of one atom of 12C divided by 12. Its approximate value is

u = (1.660 565±0.000 008 6)∙10-27 kg.

Unit CellUnit cell is the smallest fragment of the structure of a solid that by repetition can generate the entire structure.

ORThe basic structural unit of a crystal structure.

Unit OperationsThe term “Unit Operations” is used to designate an action performed on a material or a mixture of materials for a particular purpose which does not involve a chemical change (though it often does involve a physical change). The main unit operations are :

Distillation Adsorption Absorption Crystallization Extraction Heat Transfer

Unit ProcessThese are the operations, which cause Chemical changes to take place. The main Unit Processes are :

Cracking Reforming Polymerization Alkylation Isomerization Hydrogenation

Esterification Hydrolysis Hydrodealkylation Nitration

Universal Gas ConstantThe constant of proportionality appearing in the equation of state of ideal gas; defined as

R = pV/Twhere p is the pressure, V is the molar volume of the gas, an T is thermodynamic temperature.

It describes work done by 1 mole of an ideal gas when it increases its volume due to temperature increase of 1 K at constant pressure. Its SI unit is joule per mole per kelvin

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(J/mol.K). it is also known as molar gas constant or gas constant. Its value is 8.31451 m3.kPA/(kmol.K) or 8.31441 J/mol.K

Unsaturated CompoundAn organic compound that contains carbon-carbon multiple bonds. Examples include ethene and propene.

Unsaturated HydrocarbonsUnsaturated hydrocarbons are organic compounds containing double (alkenes) or triple (alkynes) bonds in its molecules.

Unsaturated SolutionUnsaturated solution is a solution that contains less than the maximum possible equilibrium concentration of a solute.

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VVacancyVacancy is a missing atom or ion in a crystal lattice.

ORA normally occupied lattice site from which an atom or ion is missing.

VacuumAny pressure less than atmospheric pressure.

ORThe full or partial elimination of Atmospheric Pressure

Vacuum DistillationA method of distillation conducted under vacuum so as to lower the boiling point of a volatile substance, usually resorted in order to avoid the decomposition or other alteration of the substance, which might occur at high temperature, or to reduce a very high boiling point to a temperature thet is more reasonably accessible in the laboratory.

Valence ElectronThe electrons in the outermost shell of an atom.

ValenceA whole number, indicating for any element its ability to combine with another element.

ValvesA valve is a mechanical device that is used to control the volume of flow and pressure of fluids. Closing, opening, or partially opening a passage through which the fluid passes regulates this flow. Fluid can be water, gas, slurry, etc. Valves are made of different materials like cast iron, bronze, steel, aluminum, plastic, ceramic and other materials. Valves are used in areas of commercial applications, domestic and process applications, automobiles, hydraulic presses, medical equipment and many more.

Although many different types of valves are used to control the flow of fluids, the basic valve types can be divided into two general groups: stop valves and check valves.Besides the basic types of valves, many special valves, which cannot really be classified as either stop valves or check valves, are found in the engineering spaces. Many of these valves serve to control the pressure of fluids and are known as pressure-control valves. Other valves are identified by names that indicate their general function, such as thermostatic recirculating valves. The following sections deal first with the basic types of stop valves and check valves, then with some of the more complicated special valves. Check Valves :These valves allow flow in only one direction. These are used in chemical process plants, water purification plants, petrochemical industries where the processed fluid is made to flow into a low-pressure area. These valves prevent reverse flow of the fluid and hence avoid contamination. When pressure in the opposite direction is applied, the valves get closed. Stop Valves :Stop valves are used to shut off or, in some cases, partially shut off the flow of fluid. Stop valves are controlled by the movement of the valve stem. Stop valves can be divided into four general categories: globe, gate, butterfly, and ball valves. Plug valves and needle valves may also be considered stop valves.

Globe Valves.- Globe valves are probably the most common valves in existence. The globe valve derives its name from the globular shape of the valve body. However, positive identification of a globe valve must be made internally because other valve types may have globular appearing bodies. Globe valve inlet and outlet

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openings are arranged in several ways to suit varying requirements of flow. Globe valves are used extensively throughout the engineering plant and other parts of the ship in a variety of systems.Gate Valves.- Gate Valves are used in process industries for full open or full close systems, when a straight-line flow of fluid and minimum restriction is desired. Gate valves are so named because the part that either stops or allows flow through the valve acts somewhat like the opening or closing of a gate and is called, appropriately, the gate. The gate is usually wedge shaped. When the valve is wide open, the gate is fully drawn up into the valve, leaving an opening for flow through the valve the same size as the pipe in which the valve is installed. Therefore, there is little pressure drop or flow restriction through the valve. Gate valves are not suitable for throttling purposes since the control of flow would be difficult due to valve design and since the flow of fluid slapping against a partially open gate can cause extensive damage to the valve. Except as specifically authorized, gate valves should not be used for throttling.

Gate valves are classified as either RISINGSTEM or NONRISING-STEM valves. On the nonrising-stem gate valve, the stem is threaded on the lower end into the gate. As the handwheel on the stem is rotated, the gate travels up or down the stem on the threads, while the stem remains vertically stationary. This type of valve almost always has a pointer-type indicator threaded onto the upper end of the stem to indicate valve position.

The rising-stem gate valve, has the stem attached to the gate; the gate and stem rise and lower together as the valve is operated.Butterfly Valves.- The butterfly valve may be used in a variety of systems aboard ship. These valves can be used effectively in freshwater, saltwater, JP-5, F-76 (naval distillate), lube oil, and chill water systems aboard ship. The butterfly valve is light in weight, relatively small, relatively quick-acting, provides positive shut-off, and can be used for throttling.

To close or open a butterfly valve, turn the handle only one quarter turn to rotate the disk 90°. Some larger butterfly valves may have a handwheel that operates through a gearing arrangement to operate the valve. This method is used especially where space limitation prevents use of a long handle.Ball Valves.- Ball valves, as the name implies, are stop valves that use a ball to stop or start the flow of fluid. When the valve handle is operated to open the valve, the ball rotates to a point where the hole through the ball is in line with the valve body inlet and outlet. When the valve is shut, which requires only a 90-degree rotation of the handwheel for most valves, the ball is rotated so the hole is perpendicular to the flow openings of the valve body, and flow is stopped.Ballcock Valves are used to control the level of water in a tank. The valve is connected to a float using a lever. The unit is placed at the top of the tank. The valve is connected to the input side of the water supply. The float rises with the water and forces the valve to shut off the valve when the maximum level is reached. It is used in water closets, water tanks and other low risk areas. Bibcock or Sillcock Valves are used in applications like building hose connections, gardening, car washing, watering lawns, and others. It has a removable control knob that when closed, presses a plug of rubber against the water passage.

Van der Waals’ BondA secondary interatomic bond between adjacent molecular dipoles, which may be permanent or induced.

Van der Waals’ EquationVan der Waals' equation is an equation of state for fluids which takes the form:

pVm = RT[{1/(Vm – b)} – a/Vm2]

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where p is pressure, Vm is molar volume, T is temperature, R is the molar gas constant, and a and b are characteristic parameters of the substance which describe the effect of attractive and repulsive intermolecular forces.

ORAn equation for non-ideal gasses that accounts for intermolecular attraction and the volumes occupied by the gas molecules.

Van der Waals’ ForcesVan derWaals' force is the weak attractive force between two molecules which arises from electric dipole interactions. It can lead to the formation of stable but weakly bound dimer molecules or clusters. They are named after the Dutch physicist Johannes van der Waals (1837-1923).

ORThese are weak interactions between MOLECULES. (Note: chemical bonds are the forces between ATOMS in a molecule whereas van der waals forces are between MOLECULES). These weak forces are caused by the attraction between protons in one molecule and electrons in an adjacent molecule. Because of the greater distance between the particles in one molecule and another, van der waals forces are only 1/100 as strong as the covalent bond.

Van’t Hoff EquationVan't Hoff equation is the equation expressing the temperature dependence of the equilibrium constant K of a chemical reaction:

d(lnK)/dT = ΔrH0/RT2

where ΔrH0 is the standard enthalpy of reaction, R the molar gas constant, and T the temperature.

Vapour PressureVapour pressure is the pressure of a gas in equilibrium with a liquid (or, in some usage, a solid) at a specified temperature.

ORVapour evaporates at the surface of a liquid. The pressure it exerts is known as vapour pressure. The higher the temperature the greater the vapour pressure.

ORThe absolute pressure, at which the liquid and its vapour are in equilibrium at a given temperature.

VelocitySpeed of an object; the change in position over time.

VirionA virus particle. Viral DNA or RNA enclosed in an organic capsule. See virus.

VirusA submicroscopic genetic constituent which can alternate between two distinct phases. As a virus particle, or virion, it is DNA or RNA enveloped in an organic capsule. As an intracellular virus, it is viral DNA or RNA inserted into the host organisms DNA or RNA.

VisbreakingVisbreaking, the term used for viscosity breaking or viscosity lowering, is a mild , liquid phase, thermal conversion process to reduce the viscosity of atmospheric and vacuum residues to produce specific fuel oil. Small quantity of LPG and fair amount of naphtha are also produced.

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ViscoelasticityA type of deformation exhibiting the mechanical characteristics of viscous flow and elastic deformation.

ViscosityResistance to flow: the ratio of the magnitude of an applied shear stress to the velocity gradient that it produces. It is denoted by μ and is also known as Absolute or Dynamic viscosity. Its unit is kg/(m.sec) or N.sec / m2

Viscosity IndexThe viscosity of a liquid decreases with increase in temperature. The change in viscosity with change in temperature is expressed by viscosity index. It is an emperical number indicating the rate of change of viscosity of oil from 100°F to 210°F. low viscosity index means a large change in viscosity with change in temperature. A high viscosity index shows relatively small change in viscosity with temperature.Viscosity Index = [(L – U) / (L – H)] X 100Where U = Viscosity of oil sample at 100°F

L = Viscosity of a standard oil of V.I. = 0, at 210°FH = Viscosity of a standard oil of V.I. = 100, at 210°F

ViscousHaving resistance to flow.

VitaminsThe name vitamins is obtained from "vital amines" as it was originally thought that these substances were all amines. This is now known not to be as vitamins have a range of structures. The body requires a small amout of vitamins, but any deficiency leads to metabolic and physical disorders.

VolatileA material which will vaporize easily.

Volatile SolidsIt is the amount of matter which volatilizes (or burns) when a water sample is heated to 550EC.

Volatile Suspended SolidsIt is the non-filterable residue remaining after firing the total suspended solids at 550EC. See total suspended solids and fixed suspended solids.

VolatilityThe tendency or ability of a liquid to pass into the vapour phase; liquids such as alcohol or gasoline, because of their tendency to evaporate rapidly, are called volatile liquids.

VoltVolt (V) is the SI derived unit of electric potential. One volt is the difference of potential between two points of an electical conductor when a current of 1 ampere flowing between those points dissipates a power of 1 watt. It is named after the Italian physicist Alessandro Volta (1745-1827).

VolumeMeasures the size of an object using length measurements in three dimensions.

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Volumetric Flow RateCalculated using the area of the full closed conduit and the average fluid velocity in the form, q = V x A, to arrive at the total volume quantity of flow. q = volumetric flow rate, V = average fluid velocity, and A = cross sectional area of the pipe.

VSSSee Volatile Suspended Solids

VulcanizationNonreversible chemical reaction involving sulfur or other suitable agent wherein cross-links are formed between molecular chains in rubber materials.

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WWaste MinimizationThe elimination or reduction of a waste prior to its generation. This is accomplished by process changes rather than waste treatment methods.

WastewaterConsumed or used water from a municipality or industry that contains dissolved and/or suspended matter.

WattWatt (W) is the SI derived unit of power. One watt is a power of one joule per second (W = J/s). It is named after the Scottish engineer James Watt (1736-1819).

ORAfter James Watt, Scottich (1736-1819). The watt is a unit of power, also described as the time rate of energy delivery of conversion.

Weak AcidWeak acid is an acid that incompletely dissociated in aqueous solution.

ORSubstances capable of donating hydrogen but do not completely ionize in solution.

ORAn acid that does not ionize completely under the conditions of interest. Examples include acetic acid, carbonic acid, and hypochlorous acid. See strong acid.

Weak BaseSubstances capable of accepting hydrogen but do not completely ionize in solution.

WeberWeber (Wb) is the SI derived unit of magnetic flux. The weber is the magnetic flux which, linking a circuit of one turn, produces in it an electromotive force of one volt as it is reduced to zero at a uniform rate in one second (Wb = V∙s). The unit is named after the German scientist W.E. Weber (1804-1891).

ORAfter Wilhelm Eduard Weber, German (1804-1891). The weber is a unit of magnetic flux.

WeightWeight is a measure of the pull of gravitational force on an object. It is directly proportional to mass.

WetlandSemi-aquatic land, that is land that is either inundated or saturated by water for varying periods of time during each year, and that supports aquatic vegetation which is specifically adapted for saturated soil conditions.

Wöhler's synthesis Wöhler's synthesis is a synthesis of urea performed by German chemist Friedrich Wöhler (1800-1882) in 1828. He discovered that urea (CO(NH2)2) was formed when a solution of ammonium isocyanate (NH4NCO) was evaporated. At the time it was believed that organic substances such as urea could be made only by living organisms, and its production form an inorganic compound was a notable discovery.

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XXSee mole Fraction

X-raysX-rays are electromagnetic radiation of shorter wavelength than ultraviolet radiation (10 -11 m to 10-9 m or 0.01 nm to 1 nm) produced by bombardment of atoms by high-quantum-energy particles. X-rays can pass through many forms of matter and they are therefore used medically and industrially to examine internal structure.

ORThese are electromagnetic radiations above the Ultra Violet in frequency that are produced when electrons strike a metal target. They are used to determine the atomic number of elements and the structure of crystals.

ORA type of radiation of higher frequency (or energy) that visible light but lower that gamma rays. Usually produced by fast electrons going through matter or by the de-excitation of excited atoms.

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YYieldIt is defined as the ratio of the moles of desired product formed to the moles of specific reactant consumed.

Yield StrengthThe stress required to produce a very slight yet specified amount of plastic strain.

Young's ModulusSee Modulus of Elasticity The ratio of stress to strain when deformation is totally elastic.

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ZZSee Gram-Equivalent Weight

ZeoliteZeolite is a natural or synthetic hydrated aluminosilicate with an open three-dimensional crystal structure, in which water molecules are held in cavites in the latice. The water can be driven off by heating and the zeolite can then absorb other molecules of suitable size. Zeolites are used for separating mixtures by selective absorption.

ZeotropeZeotrope is a liquid mixture that shows no maximum or minimum when vapour pressure is plotted against composition at constant temperature. See Azeotrope.

Zero Order ReactionZero-order reaction is a reaction for which the rate of reaction is independent of the concentration of reactants.

Zeta PotentialZeta potential (ζ) is the electric potential at the surface of a colloidal particle relative to the potential in the bulk medium at a long distance. Also called electrokinetic potential.Zeta potential (ζ) is the potential across the interface of all solids and liquids. Specifically, the potential across the diffuse layer of ions surrounding a charged colloidal particle, which is largely responsible for colloidal stability. Also called electrokinetic potential.

Ziegler ProcessZiegler process is an industrial process for the manufacture of high-density polyethene using catalysts of titanium(IV) chloride (TiCl4) and aluminium alkyls (e.g. triethylaluminium, Al(C2H5)3). The process was introduced in 1953 by the German chemist Karl Ziegler (1898-1973). It allowed the manufacture of polythene at lower temperatures (about 60 °C) and pressures (about 1 atm) than used in the original process.

Zone SettlingSee Hindered Settling

ZwitterionZwitterion is an ion that has a positive and negative charge on the same group of atoms. Zwitterions can be formed from compounds that contain both acid groups and basic groups in their molecules. It is also called ampholyte ion.

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