XVI.] ON THE THEORY OF CHEMICAL CHANGES. 429 



the proportion of one volume of each, or in some other simple 

 ratio, and the resulting species in the gaseous state occupies- 

 one volume, so that the specific gravity of the new species is 

 the sum of those of its factors. The converse of this is true in 

 division, and the united volumes of the resulting species are 

 some simple multiple of that of the parent ; in metamorphosis 

 a similar ratio is always observed. 



Aside from the apparent exceptions about to be noticed, the 

 weights of equal volumes of gases and vapors are their equiva- 

 lent weights, and the doctrine of chemical equivalents is that 

 of the equivalency of volumes. According to the atomic 

 hypothesis, these weights represent the relative weights of the 

 atoms, and as equal volumes contain the same number of atoms, 

 these must have similar volumes, so that we come at last to the 

 equivalency of volumes. As chemical combination is not a 

 putting together of molecules, but an interpenetration of masses, 

 the application of the atomic hypothesis to explain the law of 

 definite proportions becomes wholly unnecessary. Chemical 

 species are homogeneous ; tota in minimis existit natura. 

 Solution is chemical union, as is indicated by the attendant 

 condensation ; mechanical admixtures are not accompanied by 

 any change of volume. 



As two volumes of water-vapor yield one volume of oxygen 

 and two of hydrogen, this has been assumed to be the equiva- 

 lent of water and of hydrogen, while oxygen was represented 

 by one volume, whose weight was 8, that of the volume of 

 hydrogen being .5, so that the weight of the equivalent of wa- 

 ter was 9. But two volumes of hydrogen unite without con- 

 densation with two of chlorine, and the resulting four volumes 

 of hydrochloric gas are found to be equivalent to four volumes 

 of chlorine, hydrogen, or water-vapor. Hence four volumes are 

 to be taken for the equivalent of water, and it becomes H 2 2 , 

 with an equivalent of 18, corresponding to HC1, and to vola- 

 tile species generally, whose equivalents are represented by four 

 volumes of vapor ; from these, the equivalents of non-volatile 

 species are determined by comparison. 



Hydrogen, chlorine, and some other primary species offer 



