Melting Point Refractife.ppt

7/29/2019 Melting Point Refractife.ppt

1/20

Melting Point/Refractif

indexs/DSC

By : TEAM


2/20

Melting Point & RefractiveIndex

Elements of the Experiment

Melting Point

Theory and Background

Uses

Measurement Techniques & Equipment

Melting Point Range

Refractive Index

Theory and Background

Temperature Correction

Measurement Techniques & Equipment

Refractive Index, with temperature correction for a known

and unknown compounds

3/15/2013 2


3/20

Melting Point Theory & Background

Melting Point

Temperature pada kondisi transisi yang terjadi antara fase

solid dan liquid

Temperature pada saat kesrtimabangan exists antara kondisi

kristal (teratur) dan keadaan liquid (random)

Melting Point Range Onset point (temperatur rendah) ketika temperature pada

fase liquid pertama terlihat

Meniscus point ketika solid phase di dasar dan fase liquid

diatas dengan miniscus yang terlihat disebutPelting Point

The Clear point ketika semua substance menjadi liquid semua

Used as Melting Point in USA

3/15/2013 3


4/20

Melting Point Uses

Identifikasi senyawa

Mencari kemurnian dari senyawa

Melting Point Depression

Pure compounds display little, if any, melting point range,

i.e., they have sharp melting points

Mixtures of substances, i.e., the contamination of one

compound by another, whose components are insoluble in

each other in the liquid phase, display both a melting point

depression and, instead of a sharp melting point, a melting

point range The size of the melting point depression depends on the

composition of the mixture

Secara umum, 1% pengotor manghasilkan 0.5oC perberdaan

dengan yang murni.

3/15/2013 4


5/20

Melting Point

Melting Point Indicates Purity in Two Ways

The Purer the Compound, the Higher the Melting Point

The Purer the Compound, the Narrower the Melting Point Range

Melting point of A decreases as impurity B is added

Eutectic Point is the Solubility Limit of B in A; Thus, it isthe Lowest Melting Point of an A/B mixture

(Note: Sharp melting point, i.e., no range, at eutecticoint3/15/2013 5

Liquid A + B

Solid A + B

RangeClear Point

Onset Point

mp A

mp B

0% B 0% A

Temperature

Eutectic Point

mpB > mpA

MP Range


6/20

Melting Point

The Experiment

Determine the melting point range of:

Two Known Compounds

A Mixture of the Two Known Compounds

An Unknown Compound

Mixture of Unknown Compound and a Known compound.

Note: The Unknown might have to be mixed with additional

known compounds until the melting point of the known and

the known/unknown mixture match.

Identify the unknown compound.

Equipment Capillary Tubes

Mel-Temp Melting Point Apparatus (Obtain from PrepRoom)

3/15/2013 6

f i d


7/20

Refractive Index kegunaan Identifikasi senyawa

Mengukur kemurnian Latar Belakang Refractive Index is a physical property of liquids &

solids

Light travels at different velocities in condensedphases (liquids or solids) than in air.

Light travels more slowly through a denser substance.

The Wavelength of light is also different in condensedphases.

As the velocity decreases, the wavelength decreases.

The Frequency of light in condensed phases does notchange.

3/15/2013 7

f i d


8/20

Refractive Index The Refractive Index for a given medium

depends on two (2) variables:

Refractive Index (n) is wavelength () dependent.

Sumber sinar dengan perbedaan panjang gelombang di refrasikan

manjadi different extents in the same medium, sehaingga,

menghasilkan refractive indek yang berbeda.

Refractive Index (n) is temperature dependent.

sebagai perubahan temperature, density berubah; sehinga

kecepatan nya juga () changes.

Density dari medium menurun sebagai akibat kenaikan temperatur

Kecepatan cahaya dalam medium meningkat akibat temperatur naik

dan density menurun.

Ratio dari kecepatan cahaya dalam vacuum vs. speed cahaya dalam

medium menurun, sehingga, Refractive Index menurun akibat

temperatur naik.3/15/2013 8

f i d


9/20

Refractive Index For a given liquid and temperature, the ratio dari

kecepatan sinar dlm vacum (c) and kecepatan

cahaya dalam medium () adalah constant (n).

ratio kecepatan cahaya juga proporsional dengan rasiodari sinus sudut udara dan sinus sudut refraksi.

3/15/2013 9

nv

c

nV

Vliquid

air Constant

sin

sin

2

1

1 - Angle of Incidence (air)

2 - Angle of Refraction (sample)

(Index of Refraction)

(Refractive index)

R f i I d


10/20

Refractive IndexConsider two (2) media: air (or vacuum) & organic

liquid

Frequency of light in both media remains constant

Divide 1 by 2

3/15/2013 10

1 1v f

2 2=v f

v f

v f

2 2

= =f f f

(velocity) (Frequency * Wavelength)v f

R f ti I d


11/20

Refractive Index Since:

Then:

Substitute in original refractive index equation

Note: n1 for air (or vacuum) = 1.03/15/2013 11

1 1 1

2 2 2

sin v Refractive Index

sin v

2

1

nn

n

1 2

1 2

&c c

= =n n

v v

c

v ncv

nn n

2

1

n

n

1

2

R f ti I d


12/20

Refractive Index The Instrument Abbe Refractometer (Bausch

& Lomb)

Clean prisms with tissues & Methyl Alcohol BEGENTLE!!

Do not touch prism with fingers or other hard objects,use tissues

Use 3 4 drops of sample

Close hinged prisms together - Gently

Turn on the light - Preferred light source is a sodiumdischarge lamp producing yellow light at 589 nmalso called Sodium D light.

Move hinged lamp up into position

3/15/2013 12

R f ti I d


13/20

Refractive IndexAbbe Refractometer (Cont)

Rotate coarse and fine adjustment knobs on the rightside of instrument until the horizontal dividing line(may not be sharp at first) between the light upperhalf and dark lower halve of the visual field coincidewith the center of the cross-hairs.

Use eyepiece to focus cross-hairs

If horizontal line dividing light & dark areas appears asa colored band (chromatic aberration), adjust with theknurled drum knob on the front of the instrument

Press small button on left side of instrument to makethe scale visible.

Read refractive index value to 4 decimal places

3/15/2013 13


14/20

Differential Scanning

Calorimetry

Stephen Collins


15/20

Technical Group Talk

Definitions

Acalorimetermeasures the heat into or out of asample.

Adifferential calorimeter measures the heat of a

sample relative to a reference.Adifferential scanning calorimeterdoes all of the

above and heats the sample with a linear temperature

jalur.

Endothermicheat flows into the sample.Exothermicheat flows out of the sample.


16/20


Differential Scanning Calorimetry(DSC) measuresthe

temperatures and heat flowsassociated with transitions in

materials as a function of time and temperature in a

controlled atmosphere.

These measurements provide quantitative and qualitative

information about physical and chemical changes that

involve endothermicor exothermicprocesses, orchanges

in heat capacity.

DSC: The Technique


17/20


Conventional DSC

Metal

1

Metal

2

Metal

1

Metal

2

Sample Empty

Sample

TemperatureReference

Temperature

Temperature

Difference =

Heat Flow

A linear heating profile even for isothermal methods


18/20


What can DSC measure?

Glass transitions

Melting and boiling points

Crystallisation time and temperature

Percent crystallinityHeats of fusion and reactions

Specific heat capacity

Oxidative/thermal stability

Rate and degree of cureReaction kinetics

Purity


19/20


6

DSC Thermogram

Temperature

H

eatFlow

->exothermic

GlassTransition

Crystallisation

Melting

Cross-Linking(Cure)

Oxidation


20/20

Nuhun Pisan kanaPerhatosana

Melting Point Refractife.ppt

Documents