DERIVATIVES OF URIC ACID. 235 



parabanic acid, and carbonic anhydride. "When boiled 

 with baryta water or lead acetate, it is resolved into 

 mesoxalic acid (p. 158) and urea. Heated with dilute 

 acids, an evolution of carbonic anhydride takes place, 

 and alloxantine, urea, and oxalic acid are formed. 

 Nitric acid converts it into parabanic acid and carbonic 

 anhydride; lead peroxide into urea, oxalic acid, and 

 carbonic anhydride; reducing agents into alloxantine, 

 and dialuric acid. 



{TVTT2 

 NH.CO.CO.CO.OH. 



Is produced by combination of alloxan with alkalies. 

 "When baryta water is dropped into a solution of 

 alloxan at 60, until the white precipitate, which is 

 formed on the addition of each drop, is no longer re- 

 dissolved, barium alloxanate, C 4 H 2 N 2 5 Ba + 4H 2 6, crys- 

 tallizes out on cooling, in small, very difficultly soluble 

 crystals. This salt, after being washed, is decomposed 

 by sulphuric acid. The filtrate, on evaporation, at a 

 temperature below 40, yields a syrup, which solidifies 

 after a time, forming a crystalline mass. 



Alloxan ic acid forms a radiated, crystalline mass ; 

 very easily soluble ; very acid ; dissolves zinc with an 

 evolution of hydrogen ; is not changed by sulphuretted 

 hydrogen; and cannot be reconverted into alloxan. Its 

 salts are decomposed by boiling with water, yielding 

 urea and mesoxalates (p. 158). 



Parabanic acid (Oxalylurea), C 3 H 2 N 2 3 = 

 CO \ ^TTJ QQ is formed when uric acid or alloxan is 



dissolved in moderately strong nitric acid, and the solu- 

 tion evaporated to a syrupy consistence ; or when uric 

 acid is treated with manganese peroxide and sulphuric 

 acid. Occasionally it is obtained, instead of alloxan, 

 in the preparation of the latter. Crystallizes in color- 

 less, broad, very thin prisms; is permanent in the air; 

 tastes very acid ; and is easily soluble in water. It gives 

 a white precipitate, C 3 Ag 2 N 2 3 , with silver nitrate ; and 

 this, when heated with methyl iodide, yields silver 



