PREPARATION OF CARBONATE OF LEAD. 129 
lead into a sub-acetate, which is decomposed by the carbonic 
acid, forming ceruse and neutral acetate. So the whole the- 
ory consists in this: the constant action of a very small quan-' 
tity of acetic acid upon lead, converts it with the assistance of 
the oxygen of the air into oxide of lead ; this is changed to 
sub-acetate by the vinegar, and this again into carbonate, by 
the carbonic acid of the air and dung-heap. 
The theory of these three processes is then definitely the 
same. 
Mr. P. has made an experiment which plainly shows the 
part which the acetic acid plays in this operation, the presence 
of which appears indispensable. 
In a vessel of suitable Capacity he introduced a piece of 
sheet lead, which he placed upon a much smaller vessel, con- 
taining vinegar. The atmosphere of this vessel in which he 
conducted the experiment, had been artificially composed of 
carbonic acid and oxygen in the proper proportions for obtain- 
ing ceruse. After a certain time, this atmosphere had mostly 
disappeared, and there remained a quantity of ceruse, corres- 
ponding exactly to the proportion of carbonic acid and oxy- 
gen absorbed. Nearly the whole of the vinegar was recover- 
ed. A similar experiment was made, but in which formic 
acid was substituted for the vinegar, (very analogous in its 
chemical affinities to acetic acid, but not having the property 
of forming sub-salts with oxide of lead,) gave no result what- 
ever; from which Mr. Pelouze concluded that in the forma- 
tion of ceruse, the oxygen and carbonic acid are furnished at 
the expense of the air, and that the acetic acid is only useful 
by reason of its puperty of forming with the oxide of lead, 
a basic salt necessarily intermediate between the oxide of lead 
and ceruse. A. D. 
Joarn. de Pharm. 
