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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    ratios which may occur in a given case; but it is the task of experiment to confirm or correct these theoretical estimates. VIII. It will have been in general remarked on reading this Memoir that there are many points of agreement between our special results and those of Dalton, although we set out from a general principle, and Dalton has only been guided by considerations of detail. This agreement is an argument in favour of our hypothesis, which is at bottom merely Dalton’s system furnished with a new means of precision from the connection we have found between it and the general fact established by M. Gay-Lussac. Dalton’s system supposes that compounds are made in general in fixed proportions, and this is what experiment shows with regard to the more stable compounds and those most interesting to the chemist. It would appear that it is only combinations of this sort that can take place amongst gases, on account of the enormous size of the molecules which would result from ratios expressed by larger numbers, in spite of the division of the molecules, which is in all probability confined within narrow limits. We perceive that the close packing of the molecules in solids and liquids, which only leaves between the integral molecules distances of the same order as those between the elementary molecules, can give rise to more compli- cated ratios, and even to combinations in all proportions ; but these compounds will be so to speak of a different type from those with which we have been concerned, and this distinction may serve to reconcile M. Berthollet’s ideas as to compounds with the theory of fixed propor- tions.