CYANOGEN AND ITS COMPOUNDS. 333 



Dicyanogen, (CN) 2 or Cy 2 . The unsaturated radical CIST does 

 not exist as such in a free state, but combines whenever liber- 

 ated with another GN, forming dicyanogen. It may be obtained 

 by heating mercuric cyanide : 



HgCy 2 = Hg + 2Cy. 



It is a colorless gas, having an odor of bitter almonds, and 

 burning with a purple flame, folrning carbon dioxide and 

 nitrogen; it is soluble in water, and may be converted into a 

 colorless liquid by pressure ; it acts as a poison, both to animal 

 and vegetable life, even when present in but small proportions 

 in the air. 



Hydrocyanic acid, HCN or HCy = 27 ( Cyanhydric acid, Hydrogen 

 cyanide, Prussic acid}. This compound is found in the water 

 distilled from the disintegrated seeds or leaves of amygdalus, 

 primus, laurus, etc. It is also found among the products of the 

 destructive distillation of coal, and is formed by a great number 

 of chemical decompositions. For instance : 



By passing ammonia over red-hot charcoal : 



4NH 3 + 30 = 2(NH 4 CN) + CH 4 . 



Ammonia. Carbon. Ammonium Methane, 



cyanide. 



By the action of ammonia on chloroform : 



CHC1 S + NH 3 = HCN + 3HC1. 



Chloroform. Hydrocyanic Hydrochloric 



acid. acid. 



By heating ammonium formate to 200: 



NH 4 CHO 2 = HCN -f 2H 2 O. 



Ammonium Hydrocyanic Water, 



formate. acid. 



By the action of hydrosulphuric acid upon mercuric cyanide : 

 HgCy, + H 2 S = HgS + 2HCy. 



By the decomposition of alkaline cyanides by diluted acids: 



KCy -I- HC1 = KC1 + HCy. 



