CYANOGEN COMPOUNDS 159 



Alkyl Isocyanides. 



If silver cyanide be treated with alkyl iodides, isocyanides, com- 

 pounds isomeric with the above, are formed : 



CH 3 I + AgCN = CH 3 NC + Agl. 



It would thus appear that silver cyanide has a different structure 

 to potassium cyanide or that in the reaction a rearrangement occurs : 



KCN - KNC -> AgNC. 



These compounds are also formed by heating primary amines (p. 61) 



with chloroform and potash : 



CH 3 NH 2 + CHC1 3 + sKOH = CH 3 NC + aKCl + 3H 2 O. 



They are liquids with an abominable smell : on hydrolysis they 

 give the corresponding amine and formic acid : 



CH 3 NC + 2 H 2 O = CH 3 NH 2 + HCOOH. 



Cyanogen Chloride. C1CN. 



If mercuric cyanide, potassium cyanide, or hydrogen cyanide be treated 

 with chlorine, cyanogen chloride is obtained : 



KCN + CL, = C1CN + KC1. 



This compound, which is a liquid, polymerises on standing into solid 

 cyanuric chloride, C1 3 C 3 N 3 . Potash converts liquid cyanogen chloride into 

 potassium cyanate, and solid cyanuric chloride into potassium cyanurate : 



C1CN + 2KOH = KOCN + KC1 + H 2 O. 

 C1 3 C 3 N 3 + 6KOH = K 3 O 3 C 3 N 3 + 3 KC1 + 3H 2 O. 



Cyanamide. NH 2 . CN. 



Cyanamide is formed on passing cyanogen chloride into an ethereal 

 or aqueous solution of ammonia : 



C1CN + NH 3 = NH 2 . CN + HC1. 

 It is more readily obtained by the action of mercuric oxide on 



thiourea : 



/NH 2 



CS<f + HgO = HgS + H 2 O + NH 2 .CN. 

 \NH 2 



Calcium cyanamide is manufactured by passing nitrogen over calcium 

 carbide at 1000. 



CaC 2 + N 2 = CaCN 2 + C. 



Cyanamide is prepared from this salt by decomposition with aluminium 

 sulphate, filtration, evaporation in vacua and crystallisation from ether. 



Sodium cyanamide is prepared as described on p. 155. 



Cyanamide forms colourless hygroscopic crystals, easily soluble 

 in water, alcohol and ether, and melting at 40. It forms salts with 

 strong acids and also with bases. The salts with acids are decom- 

 posed by water. The calcium salt is frequently employed as an arti- 

 ficial manure. 



Cyanamide is readily hydrolysed by the action of acids forming urea : 



/NH 2 

 NH 2 . CN + H 2 O = CO( 



\NH 2 . 



By the action of hydrogen sulphide it is converted into thiourea, 

 and by ammonia it is converted into guanidine. 



