104 Dr. Henry’s Analysis of several Varieties 
The proportion of ingredients in the several kinds of mu- 
riate of soda (setting apart the impurities) appears, therefore, 
to be nearly the same in all. And as the very minute quan- 
tity of water, discovered by analysis, is not constant in the 
several varieties, it may be inferred to be rather an accidental 
than a necessary ingredient ; for in the latter case, an invari- 
able proportion might be expected, conformably to the impor- 
tant law, establishing an uniformity in the proportions of 
chemical compounds, which has been explained by Mr. 
Dalton, and confirmed by Drs. Thomson and Wollaston. 
What then, it may be enquired, is the cause of those 
differences which are acknowledged, on all hands, to exist 
among the several species of muriate of soda, so far as respects 
their fitness for economical purposes. If I were to hazard an 
opinion, on a subject about which there must still be some 
uncertainty, it would be that the differences of chemical com- 
position , , discovered by the preceding train of experiments, 
in the several varieties of culinary salt, are scarcely sufficient 
to account for those properties, which are imputed to them on 
tbe ground of experience. The stoved and fishery salt, for 
example, though differing in a very trivial degree as to the 
kind or proportion of their ingredients, are adapted to widely 
different uses. Thus the large grained salt is peculiarly fitted 
for the packing of fish and other provisions, a purpose to 
which the small grained salts are much less suitable. Their 
different powers, then, of preserving food must depend on 
.some mechanical property ; and the only obvious one is the 
.proved also by comparing the experiment of Dr. Marcet, with the results of Dr. 
Black and Klaproth, both of whom found the fused muriate of silver, from xoo 
,parts of common salt, to weigh 235 grains. 
