The Study of Mineralogy. 239 
ber thus obtained being for each body its equivalent weight. 
We thus find, as has long been suspected, that the equiva-. 
lent (or so-called molecular) weights of liquid and solid 
species are exceedingly elevated. That of water, a litre of 
which at 100° (its temperature of formation under a pres- 
sure of 760 mm.) weighs 958°78 grams, corresponds to 1192 
volumes of water vapour at standard temperature and pres- 
sure (H,O=17:96) condensed into a single volume; or to 
1192 X 17:96=21,408, approximately 21,400. Representing 
by p the empirical equivalent weight, which is really the 
specific gravity on the hydrogen basis (H,—2°0), and by d 
the specific gravity taking water —21,400 as unity, we ob- 
tain by the formula p+d=v, the reciprocal of the coefficient 
of the condensation which takes place in the passage of a 
normal gaseous species, by intrinsic contraction or polyme- 
rization, into the liquid or solid species, the specific gravity 
of which we have determined by comparison with water. 
§ 4. The reciprocal number thus got is, as we shall show, 
one of great significance. In determining the specific weight 
of any given liquid or solid species, the fact of prime impor- 
tance is not simply its specific gravity as compared with 
water, but the relation of the value thus determined to the 
equivalent weight, or, in other words, to its specific gravity 
on the hydrogen basis, It is not d, nor yet p, but the rela- 
tion p: d, as expressed by v. In the case of volatile species 
the true value of p may be known, but for the comparison 
of fixed solids, as oxyds, carbonates, and silicates, we deduce 
from the received formulas an arbitrary value for p by divi- 
ding the value calculated therefrom by twice the number 
of oxygen portions. Thus for MgO, p=40~+2; for SiO,, 
p=60-4; for Al,O,, p=102--6; for SiMg,O,, p=140+8; 
for CCaO,, p=100—6. For metalline minerals, including 
metals, and their compounds, with S, Se, Te, As, Sb, Bi, the 
value assumed for p is that got by dividing the empirical 
equivalent weight by the sum of the valencies, 
While the specific gravity of liquid and solid species is 
represented by d, the hardness, infusibility and insolubility 
or resistance to chemical change are, for related species, 
