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

Date:
1893
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. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    19/60 (page 15)
    Thus it appears evident to me that gases always com- bine in the simplest proportions when they act on one another; and we have seen in reality in all the preceding examples that the ratio of combination is i to i, i to 2, or I to 3. It is very important to observe that in considering weights there is no simple and finite relation between the elements of any one compound; it is only when there is a second compound between the same elements that the new proportion of the element that has been added is a multiple of the first quantity. Gases, on the contrary, in whatever proportions they may combine, always give rise to compounds whose elements by volume are multiples of each other. Not only, however, do gases combine in very simple proportions, as we have just seen, but the apparent con- traction of volume which they experience on combination has also a simple relation to the volume of the gases, or at least to that of one of them. I have said, following M. BerthoUet, that 100 parts of carbonic oxide gas, prepared by distilling oxide of zinc and strongly calcined charcoal, produce 100 parts of car- bonic gas on combining with 50 of oxygen. It follows from this that the apparent contraction of the two gases is precisely equal to the volume of oxygen gas added. The density of carbonic gas is thus equal to that of car- bonic oxide gas plus half the density of oxygen gas ; or, conversely, the density of carbonic oxide gas is equal to that of carbonic gas, minus half that of oxygen gas. Accordingly, taking the density of air as unity, we find gravity of oxygenated muriatic acid, which from our experiments contains no water, is exactly the same as that obtained by adding the density of oxygen gas to three times that of muriatic gas, and taking half of this sum. M. Thenard and I have also found that oxygen- ated muriatic gas contains precisely half its volume of oxygen, and that it can destroy in consequence its own volume of hydrogen.