238 DERIVATIVES OF URIC ACID. 



becomes white, and is resolved into barium alloxanate 

 and dialurate ; with silver nitrate it gives a grayish- 

 black precipitate of metallic silver. It is converted 

 into alloxan by nitric acid; by boiling with hydro- 

 chloric acid into alloxan, parabanic acid, and a diffi- 

 cultly soluble crystalline acid, allituric acid C 6 H 6 N 4 4 . 

 Heated with water to 180-190 it is decomposed, 

 forming oxalic acid, ammonia, carbonic anhydride, 

 and carbonic oxide. 



Alloxantine, dissolved in water, at the ordinary 

 temperature, is transformed, in the air, into ammonium 

 oxalurate, oxygen being absorbed and water formed. 



Dialuric acid (Tartronyl- or Oxymalonylurea), 

 OHW 2 4 = co | ^g- gO | CH.OH, is produced by the 



reduction of alloxantine, particularly when sulphu- 

 retted hydrogen is conducted for a long time into its 

 boiling solution. The solution, filtered from the sul- 

 phur, gives, with ammonium carbonate, a fine crystal- 

 line precipitate of ammonium dialurate, C 4 H 3 N 2 4 .ISrH 4 , 

 which is difficultly soluble in cold water, more easily 

 in hot : becomes red in the air. It is decomposed when 

 dissolved in warmed hydrochloric acid, and, on cool- 

 ing, the free acid separates in crystals. Further, it is 

 produced from alloxantine by the action of sodium- 

 amalgam; and by mixing a solution of alloxantine 

 with a hot solution of tin subchloride and an excess of 

 hydrochloric acid. It is prepared most easily by the 

 last method. Long needles ; moderately easily soluble 

 in water; the crystals turn red in the air, and are 

 gradually converted into alloxantine. 



When a solution of alloxan is added to a solution 

 of dialuric acid, there is formed a precipitate of allox- 

 antine. 



Hydurilic acid, C 8 H 6 K 4 6 . Is produced, together 

 with glycocol and pseudoxanthine (p. 246), by heating 

 uric acid with double its weight of concentrated sul- 

 phuric acid to 110-130, and then adding the mass to 

 a great deal of water. When a solution of dialuric 



