216 CYANOGEN COMPOUNDS. 



Cyanogen sulphide (sulphocyanic anhydride), 

 (CN) 2 S, is produced by mixing silver sulphocyanide 

 intimately with an ethereal solution of cyanogen 

 iodide ; and is extracted from the mass, which remains 

 behind after evaporation, by means of carbon bisul- 

 phide; is also formed when mercury cyanide and sul- 

 phur subchloride (S 2 C1 2 ) are shaken together. Clear, 

 rhombic plates, of a strong odor, similar to that of 

 cyanogen iodide ; sublimes at 30-40 ; fuses at 65 ; and 

 is decomposed at a higher temperature; soluble in 

 water, alcohol, and ether. In aqueous solution, and 

 even by the moisture of the air, it is quickly decom- 

 posed, a bright-yellow powder being thrown down. 

 Hydrogen, sulphuretted hydrogen, and potassium sul- 

 phide decompose it into hydrocyanic and sulphocyanic 

 acids. 



Cyanuric Acid. 

 3 3 2H 2 = CN 3 OH 3 + 2H 2 0. 



Formation. From solid cyanogen chloride or the 

 corresponding cyanogen bromide, by boiling with 

 water or alkalies. More practically by heating urea 

 until the evolution of ammonia ceases and the mass 

 becomes solid again ; or by passing chlorine over 

 melted urea at 140, and afterwards removing the am- 

 monium chloride by means of cold water. 



Properties. Colorless, rhombic prisms with a slightly 

 acid taste ; difficultly soluble in cold water (40 parts), 

 more easily in hot water and in alcohol. 



Tribasic acid. Yields three series of salts. The neu- 

 tral sodium salt C 3 K 3 3 Na 3 is almost insoluble in concen- 

 trated hot caustic soda. The cuprammonium salt is 

 particularly characteristic. An amethyst-colored pre- 

 cipitate, difficultly soluble in water and ammonia, which 

 is formed by the addition of an ammoniacal solution of 

 copper sulphate to an aqueous solution of cyanuric acid. 

 The alkaline salts are converted into cyanates by 

 heat. 



Methyl cyanurate, C 3 K 3 3 (CH 3 ) 3 , is produced by 

 the distillation of a dry mixture of potassium cyanate 



