HYDROCYANIC ACID. 
239 
stomach of dead bodies, to which I purposely added small 
quantities; I even allowed these mixtures to remain several 
months, (the vessels in which they were contained being well 
stopped,) and by my method sought for the presence of the 
poisonous acid I had added. In every case I was so fortunate 
as to find it in appreciable quantities, even after four and 
five months. I had, in truth, made use, in these experiments, 
of the prussic acid prepared according to the plan of Gea 
Pessina^ (see Journal de Pharmacie t. xvii., p. 315, and 
Traite de Pharmacie by M. Soubeiran,) which is now known 
to be capable of preservation during a long time without 
undergoing alteration,* which is not the case generally with 
the same acid obtained by other processes, for its existence is 
but ephemeral, t 
I also took animal matter from bodies which had been 
allowed to remain a long time in a state of putrefaction and 
endeavoured to determine if hydrocyanate of ammonia, or 
of any other alkali had been formed, but without success. 
I do not wish to infer, however, that this salt cannot be 
formed in decompositions of this kind; I pretend solely to 
demonstrate that that which I detected in the preceding 
mixtures was the acid purposely added by myself some time 
before. 
Finally. I gave to three frogs of large size, several drops 
of hydrocyanic acid a little diluted ; when these animals were 
dead (which occurred in about a quarter of an hour) I allowed 
them to remain untouched for two, four, and eight days, when 
I divided them into pieces and distilled them with pure 
water; the volatile product, when received by a very weak 
* I now possess a bottle half filled, which has been prepared for five 
months; it is as colourless as upon the first day, and has the same strength, 
odour, &c. 
f The method of Gea Pessina^ an apothecary of Milan, is the following: — 
Take of the ferrocyanate of potassa, 180 grammes ; sulphuric acid, at 66°, 
ninety grammes ; water 120 grammes ; add the water to the sul phuric acid , 
and the mixture thus formed to the ferrocyanate of potassa in a tubulated 
retort, to which a globular receiver is adapted, the latter is to be surrounded 
with ice and in it the acid is condensed with an excess of water. 
