VOLUMES OF ATOMS IN THE GASEOUS STATE. 129 



be viewed as decisive against the equality of the equivalent 

 volumes of the elementary gases. A volume of sulphur vapour 

 must be allowed to contain three times as many atoms as an 

 equal volume of oxygen gas, six times more than the same vo- 

 lume of hydrogen gas, and twelve times more than the same 

 volume of mercury vapour. A similar constitution cannot be 

 assigned to these vapours, unless on the assumption of Dumas, 

 that chemical atoms of the same kind may group together, and 

 form larger compound atoms or molecules, or divide into 

 smaller molecules. The molecule of hydrogen in the gaseous 

 state being the same as its chemical atom, each molecule of 

 oxygen while in the state of gas would be an aggregate of two 

 chemical atoms, and each of sulphur of six ; while mercury must 

 suffer molecular division in the state of vapour, each of its 

 chemical atoms being parted into two, in order that equal volumes 

 of these different gases and vapours should contain the same 

 number of molecules or atoms. But such views are entirely 

 speculative. 



In the farther consideration of the proportions in which 

 gases combine by measure, it will be found conducive to per- 

 spicuity to adopt the combining volume of oxygen as the unit 

 (instead of that of hydrogen as in the last table), in terms of 

 which to express the combining measures of other gases, both 

 simple and compound. The combining measure of oxygen 

 being one volume, the combining measure of hydrogen and its 

 class will be two volumes ; or the atom of oxygen gives one and 

 the atom of hydrogen two volumes of gas. Volumes of the gases 

 may be represented by equal squares with their relative weights 

 inscribed, the numbers having reference to the number assigned 

 to the oxygen volume. If that number be 100, or the atomic weight 

 of oxygen, as in column I of the table below, then the number 

 to be inscribed in each of the two volumes forming the com- 

 bining measure of hydrogen will be 6.25 or half its atomic 

 weight, the combining measure itself having the full atomic 

 weight of hydrogen, namely 12.5 ; and so of other gases, the 

 combining measure has the whole atomic weight which is 

 divided among the component volumes. But there is the reason 

 for preferring the number 1 102.6' to 100 for the standard oxygen 

 volume, that the weight of a volume of air being taken as 1000, 

 that of an equal volume of oxygen is 1102.6; and consequently 

 the corresponding number for the volume of hydrogen, 69, 



