Structure of Simpler Organic Compounds, i 3 1 



known for a long time. The actual reaction involved in 

 its formation by the above-described process is a complex 

 one and need not be discussed in detail. It was found by 

 Scheele, in 1782, that this substance on treatment with 

 sulphuric acid yields a volatile intensely poisonous acid, 

 designated prussic acid, which is now represented by 

 the formula HCN. It was afterwards recognized by 

 Gay-Lussac that this acid contains a radicle (CN) or 

 cyanogen, and that it behaves in an analogous manner to 

 the halogens. In the course of his researches, Gay-Lussac 

 succeeded in isolating cyanogen gas (CN) 2 . 



Cyanogen (CN) 2 , which forms a classical example of 

 a complex radicle, can now be obtained by a variety of 

 methods. Of particular interest in connection with the 

 structural formulae is its formation from ammonium 

 oxalate, from which it can be obtained by heating with 

 phosphorus pentoxide (to withdraw water) 



NH 4 .OCO CO ONH 4 - 4H 2 = N=C C=N 

 It can also be obtained by heating mercuric cyanide 



or by the action of potassium cyanide on cupric sulphate 



2CuS0 4 + 4KCN = (CN) 2 + 2CuCN + 2K 2 S0 4 

 (Compare the reaction 



2CuS0 4 + 4KI = I 2 + 2CuI + 2K 2 S0 4 ) 



Cyanogen is a colourless intensely poisonous gas, which 

 burns with a peach-coloured flame yielding carbon dioxide 

 and nitrogen. It is soluble in water, and the aqueous 

 solution on keeping decomposes, forming a dark pre- 

 cipitate. Of particular interest is its reaction towards 

 potassium hydroxide, with which it forms a mixture of 

 potassium cyanide and cyanate, a reaction which is 



