Law of Volumes in Chemistry. 261 



The Law of Volumes in Chemistry. l 



By T. Sterry Hunt. 



The questions regarding the so-called molecular weights 

 and volumes of liquids and solids, which are now attracting 

 the attention of chemists, can, I think, be better understood 

 if we keep in mind the principles enunciated by the writer 

 in 1853, that " the doctrine of chemical equivalents is that 

 of the equivalency of volumes," and that " the simple rela- 

 tions of volumes which Gay-Lussac pointed out in the che- 

 mical changes of gases, apply to all liquid and solid species ;" 

 so that " the application of the atomic hypothesis to explain 

 the laws of definite proportions becomes wholly unneces- 

 sary." In further illustration of this view it was said, in 

 1867, that " the gas or vapor of a volatile body constitutes 

 a species distinct from the same body in a liquid or solid 

 state ; and the liquid and solid species themselves often 

 [probably always] constitute two distinct species of differ- 

 ent equivalent weights." From this it follows that freez- 

 ing, melting, and vaporization are chemical changes. The 

 union of many volumes of a vapor or gas in a single volume 

 of a liquid or of a solid, is a process of chemical combina- 

 tion, while vaporization is chemical decomposition. . Such 

 decomposition is either with or without specific difference, 

 and examples of these two modes are seen respectively in 

 heterogeneous dissociation and in integral volatilization, 

 which latter is the breaking up or dissociation of a poly- 

 meric species into simpler forms having the same centesi- 

 mal composition. Both of these processes are subordinated 

 to the same laws of pressure and temperature, and involve 

 similar thermic changes in the relations of the bodies con- 

 cerned. In this enlarged conception of the chemical pro- 

 cess we find a solution of the problems above named, and an 

 explanation of the distinction which has been made between 

 "the chemical molecule" and " the molecule of the physic- 

 ist." That the latter has a much less simple constitution 

 than the former, as calculated from the results of chemical 



1 Also Science for September 10, 1886. 



