Foundations of the molecular theory / comprising papers and extracts by John Dalton, Joseph-Louis Gay-Lussac, and Amedeo Avogadro (1808-1811).

Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Foundations of the molecular theory / comprising papers and extracts by John Dalton, Joseph-Louis Gay-Lussac, and Amedeo Avogadro (1808-1811). Source: Wellcome Collection.

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    have a mass excessive in comparison with the molecules of simple substances. We might therefore imagine that nature had some means of bringing them back to the order of the latter, and the facts have pointed out to us the existence ol such means. Besides, there is another consideration which would seem to make us admit in some cases the division in question ; for how could one otherwise conceive a real combination between two gaseous substances uniting in equal volumes without con- densation, such as takes place in the formation of nitrous gas ? Sup])Osing the molecules to remain at such a distance that the mutual attraction of those of each gas could not be exercised, we cannot imagine that a new attraction could take place between the molecules of one gas and those of the other. But on the hypothesis of division of the molecule, it is easy to see that the com- bination really reduces two different molecules to one, and that there would be contraction by the whole volume of one of the gases if each compound molecule did not split up into two molecules of the same nature. M. Gay- Lussac clearly saw that, according to the facts, the diminution of volume on the combination of gases cannot represent the approximation of their elementary mole- cules. The division of molecules on combination explains to us how these two things may be made inde- pendent of each other. III. Dalton, on arbitrary suppositions as to the most likely relative number of molecules in compounds, has endeavoured to fix ratios between the masses of the molecules of simple substances. Our hypothesis, supposing it well-founded, puts us in a position to confirm or rectify his results from precise data, and, above all, to assign the magnitude of compound molecules according to the c