DERIVATIVES OF URIC ACID. 241 



tion being of an intense yellow color ; but slightly 

 soluble in alcohol, and insoluble in ether. Tribasic 

 acid ; usually forms salts, however, with one atom of 

 metal, and these are so stable that mineral acids can- 

 not liberate the dilituric acid from them. By heating 

 with bromine and a little water to 100 it is con- 

 verted into dibrombarbituric acid. 



Nitrosobarbituric acid (Yioluric acid), C 4 H 3 (NO) 

 N 2 O s -hH*0, is produced by the action of nitric or 

 nitrous acids on hydurilic acid. The potassium salt 

 can be most easily obtained by treating hydurilic acid 

 with potassium nitrate and alcohol with the employ- 

 ment of heat ; it is also formed by the action of potas- 

 sium nitrite on barbituric acid. From the potassium 

 salt is prepared the insoluble red barium salt by pre- 

 cipitating with barium chloride, and this, suspended 

 in hot water, is exactly decomposed by means of sul- 

 phuric acid. It crystallizes in rhombic octahedrons; 

 is moderately soluble in cold water, easily in hot. 

 Warmed with caustic potassa, it is resolved into nitroso- 

 malonic acid (p. 158) and urea; by heating with nitric 

 acid, it is converted into dilituric acid. Monobasic 

 acid. 



Potassium violurate, C 4 H 2 N 3 4 E: + 21PO. Deep 

 blue prisms or laminse ; much more soluble in hot 

 water than in cold, the solution having a violet color. 

 Caustic potassa colors the solution red. The ammonium 

 salt resembles the potassium salt. The sodium salt and 

 the salts of the alkaline earths form intensely red 

 colored crystals. The free acid produces a deep dark- 

 blue color in a solution of ferrous acetate, and on the 

 addition of alcohol the ferrous salt is deposited in six- 

 sided plates with a red metallic lustre. 



Amidobarbituric acid (Uramile, Murexan), C 4 H 3 

 (KII 2 )N 2 3 , is formed by the action of hydriodic acid 

 on violuric acid or dilituric acid ; by conducting sul- 

 phuretted hydrogen into a solution of violuric acid. 

 Can be prepared most easily by mixing a solution of 

 21 



