456 OBJECTS AND METHOD OF MINERALOGY. [XIX. 



their specific gravities. The gas or vapor of a volatile body 

 constitutes a species distinct from the same body in its liquid 

 or solid state, the chemical formula of the latter being some 

 multiple of the first ; and the liquid and solid species them- 

 selves often constitute two distinct species of different equiva- 

 lent weights. In the case of analogous volatile compounds, 

 as the hydrocarbons and their derivatives, the equivalent 

 weights of the liquid or solid species approximate to a con- 

 stant quantity, so that the densities of those species, in the 

 case of homologous or related alcohols, acids, ethers, and gly- 

 cerides, are subject to no great variation. These non-gaseous 

 species are generated by the chemical union, or identification, 

 of a number of volumes or equivalents of the gaseous species, 

 which number varies inversely as the density of these species. 

 It follows from this that the equivalent weights of the liquid 

 and solid alcohols and fats must be so high as to be a common 

 measure of the vapor-equivalents of all the bodies belonging to 

 these series. The empirical formula CjuHuoC^, which is the 

 lowest one representing the tristearic glyceride (ordinary stea- 

 rine), is probably far from representing the true equivalent 

 weight of this fat in its liquid or solid state ; and if it should 

 hereafter be found that its density corresponds to six times 

 the above formula, it would follow that liquid acetic acid, 

 whose density differs but slightly from that of fused stearine, 

 must have a formula and an equivalent weight about one 

 hundred times that which we deduce from the density of 

 acetic-acid vapor, C 4 H 4 4 . 



Starting from these high equivalent weights of liquid 

 solid hydrocarbonaceous species, and their correspondingly 

 complex formulas, we become prepared to admit that other 

 orders of mineral species, such as oxides, silicates, carbonates, 

 and sulphides, have formulas and equivalent weights corre- 

 sponding to their still higher densities ; and we proceed to 

 apply to these bodies the laws of substitution, homology, and 

 polymerism, which have so long been recognized in the chemi- 

 cal study of the members of the hydrocarbon series. The 

 formulas thus deduced for the native silicates and carbon-spars, 



