274 PREPARATION OP PURE HYDROCYANIC ACID. 
ART. LIX.— WOHLER'S PROCESS FOR THE PREPARATION OF 
PURE HYDROCYANIC ACID. 
Cyanide of potassium is prepared by fusing together 8 
parts of dry ferrocyanide of potassium, and 3 parts of pure 
carbonate of potash containing carbon (ignited cream of 
tartar), and 1 part of charcoal in fine powder in a covered 
crucible ; the mass while still warm is powdered, and placed 
in a stoppered bottle of such a capacity that when 6 parts 
of water are added the bottle is quite filled*. When the 
cyanide of potassium is dissolved, and the metallic iron is 
all deposited, the clear solution is poured into the retort a. 
The retort is connected by means of a bent tube with the 
U-shaped tube b c ; each arm of this tube is about 18 inches 
long and § to I of an inch wide. It is filled with small 
pieces of fused chloride of calcium, with the exception of 
the first one-third of b, which contains small pieces of the 
above-mentioned black cyanide of potassium. 
This tube stands in a cylindrical vessel ^of equal height ; 
from the arm c proceeds a long and rather narrow conduct- 
* The cyanide prepared by Liebig's process is less fit for the prepa- 
ration of pmssic acid; on account of the large amount of cyanate of pot- 
ash it contains, much carbonic acid is disengaged, which renders the 
condensation of the acid far more difficult. | 
