Chemistry 125: Lecture 19 October 16, 2009 Lavoisier’s Analysis (1789) Rise of the Atomic Theory (1790-1805) Lavoisier’s key concepts were conservation.

Chemistry 125: Lecture 19October 16, 2009

Lavoisier’s Analysis (1789)

Rise of the Atomic Theory (1790-1805)

Lavoisier’s key concepts were conservation of mass for the elements, and “oxidation”,

which could convert a “radical” or “base” into an acid. Elemental analysis was the

technique for determining the composition of organic compounds. Lavoisier's early

combustion and fermentation experiments showed a new, though naïve, attitude toward

handling experimental data. Dalton’s atomic theory was consistent with the empirical laws of

definite, equivalent, and multiple proportions. The basis of our current notation and of

precise analysis was established by Berzelius, but there was confusion about atomic weight

multiples.

For copyright notice see final page of this file

Elementary Treatiseof Chemistry

1789

PRESENTED IN A NEW ORDERAND ACCORDING TO MODERN DISCOVERIES

With Figures

1) Doctrine

2) Nomenclature

3) Operations

New OrderIdeas

Words

Facts

Facts: Analysis

Analysis

Since the chemical properties of the part of atmospheric air that does not support respiration were not well known, we were content to deduce the name of its base from the property of its gas to take the life of animals that breathed it : so we have named it azote, from the Greek privative, and from (zoe) life, thus the unbreathable part of air would be azotic gas.

besides it has been shown to enter also into nitric acid compounds; so one could be just as properly name it the nitrigen principle. Ultimately we had to reject a name which conveyed a systematic idea, & decided to avoid this risk of fooling ourselves by adopting the names azote and azotic gas, which expresses only a fact, or better a property, that of taking the life of animals that breathe this gas.

We have given to the base of the portion of air that supports respiration the name of oxygen, deriving it from two Greek words (oxus), acid, & (geinomai), to cause to be, because in fact one of the most general properties of this base is forming acids by combining with most substances. We shall thus call oxygen gas the combination of this base with caloric.WORD

FACT

THEORY

Caloric+

Base or Radical

Gas

Oxy-gen+

Base or Radical

Acid

we find ourselves forced to give a name. Nothing seems more convenient to us than hydrogen, that is to say, the generating principle of water, from (hydor) water, & from , (geinomai), to cause to be. We shall call the combinate of this principle with caloric hydrogen gas, & the word hydrogen alone will stand for the base of this same gas, the radical of water.

TraitéÉlémentairede Chimie

(1789)

?

The word gas is thus for us a generic name that designates the ultimate degree of saturation of whatever substance by caloric.

Lavoisier'sCompound

Radicals

ScheeleAcids

Oxidation States

Radical1°

"oxide"2°

"-ous" acid3°

"-ic" acid

4°"oxygenated

-ic" acid

Risky Prediction

Elemental Analysis by Oil Combustion

Air Supply

Oil Supply

H2OCollector

CO2

Collector

Lamp

H2OCollector

How to analyze a substance that will not burn cleanly?

e.g.grape sugar

Everyone knows how wine, cider and mead are made…

Plate X: Fermentation Apparatus

H2OAbsorptionby CaCl2

CO2

Absorption by NaOH soln.

any other Gas

Foam catcher

Sugar/Yeast/Water

I can consider the materials subjected to fermentation and the products of fermen-tation as an algebraic equation; and by in turn supposing each of the elements of this equation to be unknown, I can derive a value and thus correct experiment by calculation and calculation by experi-ment. I have often profited from this way of correcting the preliminary results of my experiments.

Fermentation

it can furnish a meansof analyzing sugar

Oxidationhad failed with

AirOxygen

Sulfuric AcidMercuric Oxide

etc.because of incomplete combustion (charring)

Lavoisier’s Bookkeeping

72 grains = 1 gros8 gros = 1 ounce = 28.35 g

Proximate

Ultimate

Lavoisier’s BookkeepingProximate

Ultimate

Lavoisier’s Bookkeeping

after

before

Hydrogen GeneratorRed-hot Glass Tube

Water

28 grains Carbon

Water

Water (less 85.7 grains)

144 cu. in. (100 grains) Carbonic Gas380 cu. in. (13.7 grains) Flammable Gas

Carbon + Water 28 gr. 85.7 gr.

= Carbonic Gas + "Hydrogen" 100 gr. 13.7 gr.

"I have thought it best to correct by calculationand to present the experiment in all its simplicity."

157

313

103

9.4from 28 gr. C

(modern theory)

?+ += !

1.38 g

Traitépp. 88-92

Facts Ideas

Words

Lavoisier Contributions

Elements

Conservationof Mass

Oxidation

Radical/Acid

Salts

Apparatus

QuantitationMassvolume

Substances

Reactions

Meaningful NamesElement - Oxidation State - Salt Composition

-ous, -ic, -ide, -ite, -ate

Clarity

[Chemistry's] present progress, however, is so rapid, and the facts, under the modern doctrine, have assumed so happy an arrangement, that we have ground to hope, even in our own times, to see it approach near to the highest state of perfec-tion of which it is susceptible.

Lack of Imagination

"It took them only an instant to make

this head fall, but a hundred years

may not suffice to reproduce one like it."

"Il ne leur a fallu qu’un moment pour faire

tomber cette tête, et cent années peut-être ne suffiront pas pour

en reproduire une semblable."

Lavoisier Guillotined May 8, 1794 Age 50

"The Republic has no need of geniuses.”

But all of his equipment (including 80 pounds of mercury)

was seized for The People.

Boyle Lavoisier√

√

John Dalton

Why do gases of different density remain mixed rather

than stratifying?

amateur meteorologist

1801

Continental European scientists proposed that different gases attract one another.

"the atoms of one kind did not repel the atoms of another kind"

Atom“Heat Envelope”

Match

Repulsion

Mismatch

Reduced

Repulsion

Substituteshomorepulsion

for heteroattraction

Atoms Explain:

Definite Proportions

Equivalent Proportions

Multiple Proportions

Pure compounds always have the same weight ratio of their elements.

If a parts of A react with b parts of B,and a parts of A react with c parts of C,…

If two elements form several compounds,their weight ratios are related by simple factors.

and d parts of D react with b parts of B,then d parts of D react with c parts of C.

=

Definite Proportions?

Joseph Louis PROUST(1754-1826)

Claude Louis BERTHOLLET

(1748-1822)

NON! OUI !

metal alloysnatural "organic" materials "chemicals"

Multiple Proportions

O/C

2.57

1.27

O/N

0.58

1.27

2.39

Oxides of Carbon %C %O

28 72

44 56

Carbonic Acid (1801)

Carbonous Acid (1789)

Oxides of Nitrogen %N %O

63.30 36.70

44.05 55.95

29.50 70.50

Nitrous Oxide (1810)

Nitrous Gas (1810)

Nitric Acid (1810)

[1]

2.19

4.12

2.02

[1]

Rel.

Rel.

integral values consistent with simple atomic ratios%err

of (O/C)vs. modern

-4

-5

-2

+11

+11

%errof (O/N)vs. modern

Great scientists focus on the key factors despite errors.(Greatness : Key :: Chicken : Egg)

~2

~4

~2

Genealogy Top

Berzelius etc.

√

BerzeliusJöns-Jakob

BERZELIUS(1779-1848)

Organic & Mineral

Analysis

Dualism(double decomposition)

Electrolysis

Notation forComposition

Teaching, Writing& Editing

Textbook(1808)

2000 compounds in 6 years!

Good Atomic Weightsfor 50 elements!

Notation for Composition

Alchemy

Dalton

Berzelius

ChemicalSymbolsof 1774(Sweden)

1774 Symbols

“When only one combination of two bodies can be obtained, it must be pre-sumed to be a binary one, unless some other cause appear to the contrary.”

ChemicalSymbolsof 1774(Sweden)

HO HN NO HC OC

N2O NO2 CO2 CH2

H N C O P S Mg CaNa K Sr Ba Fe Zn Cu Pb

Ag Pt Au Hg(Corresponding Berzelius Symbols)

Dalton Notation(1808)

http://webserver.lemoyne.edu/faculty/giunta/dalton.html

NO3 SO3 SH3 C3H

“When four…one binary, two ternary, and one quarternary, &c.

Latin (international)

Analytical (NOT structural)

Berzelius Notation(1811)

Dalton’s Logic

N2O NO2 CO2 CH2

NO3 SO3

SH3 C3H

When three…a binary, and the other two ternary. ”

“When two combinations are observed, they must be presumed to be a binary and a ternary…

Abbreviations: Dots denote O atoms

= KO CrO3

Superscripts denote numbers of atomsBenzoic should be H10C14O3 (“acid” as anhydride)

Didn’t catch on

End of Lecture 19Oct. 16, 2009

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