$52 Experiments ,on Prussic Acid.. (May, 
strated, several distinguished chemists have entertained. doubts re- 
specting its composition. Even Berthollet himself seems to partake 
of these ; for he thus expresses himself in his Statique Chimique, 
vol. ii. p. 267 : ‘* These considerations do not constitute a rigorous 
proof of the absence of oxygen in prussic acid, and we ought to sus- 
pend our opinion on this subject, till pure prussic acid has been 
analyzed. ‘The following observations even add to our uncertainty. 
However, in the explanation which I am going to give, I shall em- 
ploy the hypothesis that it contains no oxygen in its composition.” 
From the analogy which subsists between prussic acid and sul- 
phureted hydrogen, but particularly from the remark that the 
prussiates are decomposed by a heat not sufficient to form the 
alkaline ley of Prussian blue, M. Berthollet admits likewise (Stat. 
Chim. vol. ii. p. 267) that during the calcination of potash with 
animal matters, there is formed a combination of the alkali, carbun, 
and azote, which decomposes water when it comes in contact with 
it, and forms carbonic acid, ammonia, and prussic acid. This com- 
bination in fact takes place; but it is not demonstrated by the 
considerations employed by Berthollet ; for the simple prussiate of 
potash is capable of bearing a very high temperature without losing 
the property of precipitating the solutions of iron blue; and we 
shall see that when the product of the calcination of potash and 
animal matters is dissolved in water, ammonia is only formed when’ 
it is thrown into the water when still red-hot. 
Curaudau, without being acquainted with the work of Berthollet 
which was printed, but not published, when he read his memoir to 
the Institute, was led to the same opinion respecting the nature of 
the compound formed during the calcination of potash with animal. 
matters. But his theory is so hypothetic, that I would take no 
notice of it, unless I were afraid that an hasty examination might 
find some resemblance between his opinions and a part of mine. 
According to Curaudau, there exists a prussic radical, to which he 
gives the name of prussine, which is common prussic acid. This 
radical, by combining with oxygen, forms true prussic acid and its 
combinations, the prussiates. It acquires the neutralizing or acid 
properties only at the expense of the oxygen furnished by a metallic 
oxide, the presence of which is necessary to form with the acidifi- 
able bases a strong and Jasting compound. When an animal matter 
is calcined with potash, a compound is formed, which is nothing 
else than carbureted azote of potash. When dissolved in water, 
carbonic acid is produced at the expense of the oxygen of the water, 
and part of the carbon, while the hydrogen with the rest of the 
carbon and azote forms the prussine (Ann. de Chim. vol. xlvi. 
p- 148). 
The most recent memoirs on prussic acid with which I am ac- 
quainted are those of Mr. Porrett, an extract of which may be 
found in the fourth and fifth volumes of Dr. Thomson’s Annals of 
Philosophy. In the first Mr. Porrett treats of the triple prussiates. 
According to him, they contain, not prussic acid, but an unknown 
