PREPARATION OF PURE HYDROCYANIC ACID. 275 
ing tube, bent at a right, or any other convenient angle, into 
the vessel e ; by means of the caoutchouc tubes / /J the ap- 
paratus is made more safe. When the apparatus is thus 
disposed, and all the junctions and corks found to be per- 
fectly tight, the cylinder d is filled with ice-cold water, and 
the small and narrow flask e, destined to receive the acid, 
is immersed in snow or ice and salt, up to the neck. 
A cold mixture of equal parts of sulphuric acid and water 
is now poured through the funnel into the cyanide of pot- 
assium in the retort in very small successive portions ; for 
2 parts of the melted mass of cyanide of potassium 1 part 
of oil of vitriol is taken ; the mass in the retort is so highly 
heated by this addition of the dilute acid as to begin to boil ; 
the acid must therefore only be added at long intervals, 
taking care that no air enters with it. It is probable that a 
concentrated solution of tartaric acid would be preferable to 
the sulphuric acid. During the addition of the sulphuric 
acid a considerable quantity of prussic acid is developed, 
which would be carried out of the apparatus along with 
air; to avoid this the chloride of calcium tube is placed in 
cold water and the recipient in ice. When all the acid has 
been added, and the fluid in the retort no longer boils, the 
cold water is removed from the cylinder d by means of a 
siphon, and replaced with water at a temperature of 85° to 
90° F. By this means the prussic acid previously conden- 
sed in the chloride of calcium tube is evaporated, and passes 
into the recipient e ; at the same time the contents of the 
retort are brought to gentle ebullition, which is continued as 
long as prussic acid is disengaged. The tube f may be sur- 
rounded with ice also, when conveniently bent, so as to 
render the condensation of the acid more certain. Without 
the use of ice the preparation of the anhydrous acid should 
by no means be attempted ; and even then, the operations 
and all experiments with this substance, should be conduct- 
ed with the greatest care and precaution. — Chem. Gaz.from 
Ilaudworterbuch der C hemic 
