80 HUNT: MINERALOGICAL SUPPLEMENT. 
bable that the lower densities found for some other calcites may correspond to isomeric 
species with smaller coefficients of condensation. Aragonite has the formula 860(CCaO,) = 
86,000, with a calculated specific gravity of 2,934. 
Differences in specific gravity like those seen between the isomeric species, calcite 
and aragonite, appear in the hydrocarbons of the terpene group, which, with a common 
centesimal composition, constitute several species differing widely in specific gravity and 
in boiling point, but interconvertible. Analogous differences in specific gravity and in 
boiling point are noticed in the isomeric propylic and butylic alcohols, and correspond 
to greater or less degrees of condensation. 
$ 22 From the above principles, we find :— 
I. The equivalent weight for liquids and for solids, as for gases, varies directly as 
the density, so that having determined this weight for water (which is here made the 
unit of density for gases as well as for liquids and solids) we are enabled to calculate it 
for any species the density of which is known. 
II. The value of the chemical unit being either fixed experimentally, as in the case of 
vapors, or assumed, as in the case of non-volatile species, we, from the equivalent weight 
of the species, determine the coelficient of the condensation therein. ‘i 
III. The value got by dividing the equivalent weight of the chemical unit by the 
density of the species, is the reciprocal of the coefficient of condensation of that unit; 
being called, in the language of the molecular hypothesis, the volume of the chemical unit 
or molecule. 
