Chem 125 Lecture 21 10/21/05 Projected material This material is for the exclusive use of Chem 125 students at Yale and may not be copied or distributed further. It is not readily understood without reference to notes from the lecture.
Genealogy Top
Elementary Treatise of Chemistry 1789 PRESENTED IN A NEW ORDER AND ACCORDING TO MODERN DISCOVERIES With Figures
Clarity: FactsIdeas Words “impressions of the same seal”
New Order 1) Doctrine 2) Nomenclature 3) Operations
Elements: Operational Definition …if by the name of elements we mean to desig- nate the simple, indivisible molecules that make up substances, it is probable that we do not know what they are : but if, on the contrary, we associate with the name of elements, or of the principles of substances, the idea of the furthest stage to which analysis can reach, all substances that we have so far found no means to decompose are elements for us…they behave with respect to us like simple substances.
Traité É lémentaire de Chimie (1789) Table of Elements imponderable
Lavoisier-Laplace Calorimeter Flame Melting Ice Insulating Ice 3 Feet
Facts: Analysis
Analysis
Traité É lémentaire de Chimie (1789) ? WORD FACT THEORY Oxy-gen + Base or Radical Acid
Lavoisier's Compound Radicals Scheele
Oxidation States Radical 1° "oxide" 2° "-ous" acid 3° "-ic" acid 4° "oxygenated -ic" acid
Elemental Analysis by Oil Combustion Air Supply Lamp Oil Supply H 2 O Collector CO 2 Collector
Fermentation
Plate X Fermentation Apparatus
Oxidation failed with air oxygen sulfuric acid mercuric oxide etc. 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 means of analyzing sugar
Bookkeeping
Hydrogen Generator Red-hot Glass Tube Water 28 grains Carbon Water Water (less 85.7 grains) 144 cu. in. (100 grains) Carbonic Gas 380 cu. in. (13.7 grains) Flammable Gas Carbon + Water 28 gr gr. = Carbonic Gas + "Hydrogen" 100 gr gr. "I have thought it best to correct by calculation and to present the experiment in all its simplicity." modern theory
FactsIdeas Words Lavoisier Contributions Elements Conservation of Mass Oxidation Radical/Acid Salts Apparatus Quantitation Mass volume Substances Reactions Meaningful Names Element - 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. Imagination
Boyle Lavoisier
John Dalton Why do gases of different density remain mixed rather than stratifying? amateur meteorologist 1801 Continental Europeans proposed hetero-attraction, but Dalton preferred Newtonian repulsion.
"the atoms of one kind did not repel the atoms of another kind" Atom Heat Envelope substitutes homorepulsion 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, and d parts of D react with b parts of B, then d parts of D react with c parts of C. If two elements form several compounds, their weight ratios are related by simple factors.
Definite Proportions? Joseph Louis PROUST ( ) Claude Louis B ERTHOLLET ( ) NON!OUI ! metal alloys natural "organic" materials "chemicals"
Multiple Proportions O/C O/N Oxides of Carbon%C%O Carbonic Acid (1801) Carbonous Acid (1789) Oxides of Nitrogen%N%O Nitrous Oxide (1810) Nitrous Gas (1810) Nitric Acid (1810) %err (1) (~2) (~4) (~2) (1) Rel. integral values consistent with simple atomic ratios
Genealogy Top
End of Lecture 21