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
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.
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)
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.
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
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!
“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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