With few exceptions, the new chemistry of Lavoisier was adopted by chemists everywhere. With the nature of the airs,
metals,
and earths
understood, chemists turned their attention to determining the composition of compounds, and the nature of what holds them together. European chemists rapidly collected data based on the new definition of element. They found that typically each substance was combined in only a single set ratio of component mass or volume (when constrained to constant temperature and pressure). As we might expect in retrospect, there was some confusion caused by several complicating factors.
Joseph Louis Proust (1754 to 1826 at right→), teaching at Madrid in 1799 showed that the composition of copper carbonate is fixed, no matter where it is obtained or how it is synthesized. Over the next 9 years he purified and analyzed numerous compounds, collecting data to support the Law of Constant Proportions.
Claude Louis Berthollet (1748 to 1822 ←at left), a collaborator with Lavoisier on the new nomenclature, approached chemical composition in his books Recherches sur les lois de l'affinite
(1801) and Essai de statique chimique chimique
(1803) as a matter of chemical affinities similar to gravity. Believing that there is no difference between solutions and compounds, he argued that Proust's law of constant proportions was an accidental effect of saturated solutions.
However, by 1808 Proust's Law of Constant Composition was accepted by nearly all chemists.
John Dalton (1766 to 1844 at right→) of Manchester, as part of a life-long series of weather observations and research on gases, speculated upon the nature and constitution of the atmosphere. Fellow Englishman, Issac Newton, earlier developing the physics of a gas, treated it as an elastic fluid composed of small particles (or atoms) repelled by an inverse square force much as he had considered gravity as an attractive inverse square force. It occured to Dalton to contemplate the effect of the difference of size of the particles in such a fluid under different pressures and temperatures. He tried to determine the relative sizes and weights of atoms from the numbers of atoms in a given volume. This led to consideration of combinations of gases and the numbers of atoms in such combinations.
In 1801 Dalton applied the atomic concept to account for a mixture of gases exerting a pressure equal to the sum of the partial pressures. (I.e., each gas exerts its own pressure independent of other gases.) In 1803 he announced that the amount of gas dissolved in water from a mixture of gases is proportional to the partial pressure of that gas.
In studying two gases made of only carbon and hydrogen, olefiant gas
and carburetted hydrogen,
Dalton found the latter had exactly twice as much hydrogen in relation to carbon. After applying the procedure to carbonic oxide,
ammonia, and water, he published in 1808 New System of Chemical Philosophy
describing how the Atomic Theory could account for chemical compositions. In short, Dalton combined the Atomic Theory with Lavoisier's new definition of element, two ideas previous considered contradictory, to explain the Law of Constant Composition.
Dalton listed the atomic weights of each element relative to the lightest element, hydrogen, being set equal to 1. In determining relative weights, Dalton relied on the results of quantitative analysis of compounds, and the assumed formulas for the compounds. Dalton presumed the simplest of formulas: thus water was composed of one atom hydrogen to one atom of oxygen.
If you need course credit, use your observations recorded in your journal to construct a formal report.
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