HYDROCYANIC ACID, &C. 
163 
then, by some accident or other cause, taken to where Allen's 
acid was used, a sudden, and I fear, a fatal increase would be 
the result, for more than a triple quantity would be taken. 
For the possibility of a fatal accident I need only refer to the 
case of seven individuals near Paris being killed by a slightly 
increased dose, recorded in all the medical periodicals a few 
years since. 
On the same evening I called the attention of the members 
of the Medico-Botanical Society to the method for procuring 
medical hydrocyanic acid recommended by Dr. Thomas 
Clarke, by cyanide of potassium and tartaric acid; a method 
which can now be employed by any one, since Mr. Laming has 
brought into the market a very pure salt. From very nume- 
rous trials, I find that the procuring of this salt, the cyanide 
of potassium perfectly pure, must be expensive, and I have 
never been able to procure it strictly in this state without 
using alcohol to crystallize it from; and many chemists, I 
find (see Mr. Barry's paper above alluded to) object to it, 
from its being so excessively deliquescent, and hence rather 
unmanageable, and also to the liability of this highly poison- 
ous salt being mistaken for other white salts on their counters. 
This latter objection, I must say, is hypocritical: if people 
will be careless there is no means of preventing mistakes, and 
I conceive the objection of Mr. Barry applies with tenfold 
force to many arrangements of a druggist's shop, where we 
often see tincture of opium flanked right and left by other 
dark tinctures; and who that has manipulated has not caught 
himself laying hold of, and using one acid, &c. for another, 
when the mind is also at work? 
I have made many trials as to the practicability of applying 
the cyanide of silver and dilute hydrochloric acid for procur- 
ing medical hydrocyanic acid. The cyanide of silver pre- 
sents many advantages: it is perfectly stable, being neither 
affected by light nor moisture; its purity can be very easily 
ascertained, and every five grains of it will yield one grain of 
acid. It can be procured by conducting the vapour from the 
process described above into a pint of water, holding 255 
