T. S. Hunt on the Theory of Chemical Changes. 231. 
is often,a multiple by some whole number, of that calculated 
from the results of ultimate analysis. As the equivalents of non- 
Volatile Species are generally assumed to be those quantities which 
Sustain the simplest ratio to certain volatile ones, the rea equiva- 
lent weight corresponding to four volumes of vapor, and conse- 
quently the theoretical vapor-density of such species, is liable to 
adegree of the same uncertainty as those deduced from ultimate 
analysis. Having, however, determined the true equivalent of a 
species, from the density of its vapor, the inquiry arises whether 
4 definite and constant relation may not be discovered between 
ls vapor-density, and the specific gravity of a species in the solid 
Sate. Such a relation being established, and the value of the 
condensation in passing from a gaseous to a solid state being 
known, the equivalents of solids, like those of vapors, might be 
tmined from their specific gravities. 
- Aconnection between equivalent weight and density is evident 
NM some allied and isomorphous species. H. Kopp, in dividing 
“we assumed equivalent weights of such bodies by their specific 
Stavities, obtained quantities which were found to be equal for 
Some of these related species. These numbers evidently rep- 
tésent the volumes of equivalents, and in accordance with the 
#omic hypothesis, are said to denote the atomic volumes. The 
nguiry of Kopp has been pursued by many investigators, among 
whom are Schroeder, Filhol, Playfair and Joule, and more recently, 
Dana, Their results show that the volumes thus calculated for 
related Species of similar crystallization, are generally ident 
PF sustain to each other some simple ratio; while Mr. Dana, who 
has compared isomorphous species of unlike chemical constitu- 
Non, finds that the calculated volumes are often to each other, as 
~ © humber of equivalents of elements, in the formulas represent- 
ing the Species; thus leading to the conclusion that the real 
} 
“quivalent Weight is either a mean of that of all the elements, or 
i ights of these by the number of elements, are nearly equal. 
ey divide by the number of elements, the equivalents calcu- 
1p €quivalents vary with the specific gravity. : 
hese investigations have been principally confined to native 
‘40d artificial mineral species, and the equivalents have been cal- 
eilated from the formulas of Berzelius and Rammelsberg, which 
*88.the simplest ratios deducible from analysis. While in 
wuformity With the dualistic notions, a mineral like calcite or 
Pg Was regarded as a compound of one equivalent of car- 
“© acid and one of lime or magnesia, dolomite was said to be 
