DERIVATIVES OF URIC ACID. 239 



acid in glycerin is heated to 140-150, it is resolved 

 into carbonic anhydride, formic acid, and acid ammo- 

 nium hydurilate. The same salt is produced by boil- 

 ing alloxantine with very concentrated sulphuric acid. 

 In order to separate the acid, the salt is dissolved in 

 boiling water with ammonia, and to the filtered solu- 

 tion, copper sulphate added. From the dark-green 

 solution are deposited black, anhydrous crystals, if the 

 solution was still hot on the addition of the copper 

 sulphate; if the solution was cold, red crystals, con- 

 taining water, are deposited ; in both cases the crystals 

 consist of the neutral copper salt. This is thrown 

 into hot hydrochloric acid, the crystalline hydurilic 

 acid, which separates, washed with dilute hydrochloric 

 acid, and recrystallized from water. It crystallizes 

 from water in small four-sided columns with two mole- 

 cules of water of crystallization ; from its salt, on the 

 addition of hydrochloric acid, with the aid of heat, it 

 separates in small, rhombohedric plates with one mole- 

 cule of water. Difficultly soluble in water and alcohol. 

 Strong, bibasic acid. The solutions of the acids and 

 its salts become colored a beautiful dark green on the 

 addition of a solution of iron sesquichloride. A mix- 

 ture of hydrochloric acid and potassium chlorate con- 

 verts it into dichlorhydurilic acid, C 8 H 4 C1 2 N 4 6 . Fuming 

 nitric acid converts it into alloxan ; ordinary nitric acid 

 yields, in addition to this, violuric acid, violantine, and 

 dilituric acid. When heat is employed only the last 

 acid is produced. 



Barbituric acid (Malonylurea), C 4 H 4 N" 2 3 = 

 ^ I OTl'cO ( ^H 2 - -^7 heating a solution of alloxan- 

 tine in three to four parts concentrated sulphuric acid 

 on a water-bath, until the evolution of sulphurous anhy- 

 dride has ceased, there is obtained a honey-colored solu- 

 tion, which becomes thick on cooling. When this is 

 diluted with an equal volume of water, an abundant 

 precipitate of a difficultly soluble body is obtained, 

 which is completely dissolved by boiling with water. On 

 the cooling of this solution barbituric acid crystallizes 



