PHARMACEUTICAL NOTICES. 
259 
ART. LXX.— PHARMACEUTICAL NOTICES. 
By William Procter, Jr. 
Mote on the preparation of Hydrocyanic Acid. 
The formula for hydrocyanic acid in the United States 
Pharmacopoeia, was adopted by the revisers of that work 
from the last London Pharmacopoeia. It is founded on that 
of Gea Pessina for the strong acid, and is the best and most 
economical of all that have been proposed. 
The Pharmacopoeia directs : 
Ferrocyanuret of Potassium (yellow Prussiate of 
Potash) ^ij. 
Sulphuric acid, giss. 
Distilled water, a sufficient quantity. 
The acid is mixed with four fluid ounces of the distilled 
water and poured into a glass retort. The prussiate of 
potash is then dissolved in ten fluid ounces of distilled water 
and added to the diluted acid. Half a pint of distilled water 
is poured into a well refrigerated receiver, adapted to the 
retort, and heat applied to the latter by means of a sand 
bath until six fluid ounces of liquid have distilled. The 
fourteen ounces of solution of hydrocyanic acid thus obtained 
in the receiver, is stronger than 2 per cent., and is directed 
to be diluted until 100 grains of it is of such strength as to 
accurately saturate 12*7 of nitrate of silver. 
In remarking on this well established formula, it is with 
no view of changing it, but merely to suggest a few practi- 
tical directions not found in the books, and the result of 
much experience. It may be observed that the directions 
of the Pharmacopoeia in reference to the use of distilled 
water should be adhered to, at least so far as the water in 
the receiver and the water of dilution are concerned. Our 
Schuylkill water sometimes contains sufficient oxide of iron 
to cause, by standing, a minute deposite of Prussian blue in 
the acid. In a globular receiver it is difficult to tell jusl 
