548 CONSIDERATION OF CARSON COMPOUNDS. 



The name cyanogen signifies " generating blue/' in allusion to the 

 various blue colors (Prussian and TurnbulPs blue) containing it. 



Cyanogen and its compounds show much resemblance to the halo- 

 gens and their compounds, as indicated by the composition of the 

 following substances : 



Dicyanogen, (CN) 2 . The unsaturated radical CN does not exist 

 as such in a free state, but combines whenever liberated with another 

 CN, forming dicyanogen. It may be obtained by heating mercuric 



cyanide : 



Hg(CN) 2 = Hg + 2CN. 



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

 ing with a purple flame, forming 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 = 26.84 (Prussic acid). This compound 

 is found in the water distilled from the disintegrated seeds or leaves 

 of amygdalus, prunus, laurus, etc. It is also found among the prod- 

 ucts of the destructive distillation of coal, and is formed by a great 

 number of chemical decompositions. For instance : 



By the action of ammonia on chloroform : 



CHC1 3 + NH 3 : HCN + 3HC1. 

 Chloroform. Hydrocyanic Hydrochloric 



acid. acid. 



By heating ammonium formate to 200 C. (392 F.) : 



NH 4 CH0 2 : HCN + 2H 2 0. 

 Ammonium Hydrocyanic Water, 

 formate. acid. 



By the action of hydrogen sulphide upon mercuric cyanide : 



Hg(CN), + H 2 S = : HgS + 2HCN. 



