251 
which depend on Weak Affinities. 
tated by an excess of the alkaline carbonate, it seemed to con-* 
tain a small quantity of this carbonate ; and the result was si- 
milar, whether the carbonate of potash or of soda was employ- 
ed. In different experiments the carbonate of zinc, when pre- 
cipitated by carbonate of potash, in the smallest possible excess, 
gave from 73.15 to 73.25 per cent, of oxide of zinc. When the 
liquid contained more alkali, I found from 73.6 to 73.7 per cent 
of residuum. In the latter case, the oxide, after cooling, was 
perfectly white ; but in the former it had a slight tint of very 
pure yellow. The oxide of zinc, which I used for these expe- 
riments, had been separated, by evaporation, from a solution of 
this oxide in caustic ammonia. It was then dissolved in an 
acid, and by adding to the solution a carbonate, sometimes of 
potash, sometimes of soda, the oxide was changed into the car- 
bonate of zinc. Having analysed this carbonate in the appara- 
tus used for the magnesia, I found 
Oxide of zinc, - - 73.15 
Carbonic acid, - - 14.72 
Water, - - - 12.13 
I made several experiments, but their results varied so little, 
that it is unnecessary to detail them. The oxygen contained in 
the oxide of zinc is 14.344 ; whilst that of the carbonic acid is 
10.695, and that of the water 10.704. The two last quantities 
are thus equal : but the oxygen, in the oxide of zinc, is to that 
in the carbonic acid as 4 to 3 ; a ratio which does not occur 
either in blue carbonated copper or magnesia alba, and which 
affords another proof in favour of those opinions which I have 
explained above. If we consider the substance now analysed, 
as consisting of the hydrate combined with the carbonate of 
zinc, it will appear to contain one molecule of a hydrate of the 
oxide of zinc, in which the water has 3 times the oxygen of the 
base, and 3 molecules of a carbonate, in which the oxide and 
the acid contain equal quantities of oxygen. It is represented 
by the formula, Zn Aq® -{- 3 Zn C* ; and by calculation th^ fol- 
lowing result is deduced from it : 
Oxide of zinc, - - 73.04 
Carbonic acid, - - 14.79 
Water, _ - - 12.17 
* Zn represents 1 atom of zinc combined with 2 atom.s of oxygen. 
