CYANOGEN COMPOUNDS. 221 



of the filtered solution, a white, easily-detonating salt 

 C 2 N 2 2 .KAg crystallizes out. 



Fulminuric acid (Isocyanuric acid), C 3 H 3 ISF 3 3 . 

 The alkaline salts are produced, together with mercury 

 chloride or iodide, by boiling fulminating mercury 

 with chlorides or iodides of the alkalies. The free 

 acid, separated from the lead salt by means of sulphu- 

 retted hydrogen, crystallizes in small prisms ; soluble 

 in water, alcohol, and ether; explodes when heated to 

 145. Monobasic acid. When added to a cooled 

 mixture of very concentrated nitric and sulphuric 

 acids, it yields carbonic anhydride, ammonia, and tri- 

 nitroacetomtrile C 2 N 4 6 = C(K0 2 ) 3 .CK Colorless, crys- 

 talline, camphoraceous mass, which fuses at 41.5, ex- 

 plodes when heated above 200, and is decomposed by 

 water and alcohol even at the ordinary temperature. 

 (See Nitroform, p. 36.) 



Allophanic acid, C 2 H 4 N 2 3 . ISTot known in a free 

 state. Is decomposed, at the instant of its liberation, 

 into urea and carbonic anhydride. Its ethers are 

 formed by conducting the vapor of cyanic acid into 

 anhydrous alcohols. 



Ethyl allophanate, C 2 II 3 X 2 3 .C 2 IP. Colorless 

 prisms, soluble in alcohol and hot water. Is resolved 

 by distillation into alcohol and cyanuric acid. When 

 mixed with barium hydroxide. and water, it yields 

 barium allophanate (C 2 HM 2 3 ) 2 Ba. 



Biuret (Allophanamide), C 2 H 5 ST 3 3 + H 2 0. Is 

 formed by heating ethyl allophanate with aqueous am- 

 monia to 100 ; and by heating urea to 150-160. 

 Long, colorless needles; fusing point, 190; pretty 

 difficultly soluble in cold water, easily soluble in hot 

 water and in alcohol. Heated above its melting point, 

 it is decomposed, yielding ammonia and cyanuric acid. 

 When copper salts or caustic potassa are added to its 

 solution, it turns red. 



Trigenic acid, C 4 H 7 N 3 2 , is produced when cyanic 

 acid vapor is conducted into well-cooled aldehyde, a 



