58 ORGANIC CONSTITUENTS. 



verted by hyponitrous acid into water, carbonic acid, and 

 nitrogen. Hence, if we suppose that the 2 atoms of uril 

 (bearing in mind that uric acid =^ 2U1. + 1 at. urea,) take up 

 the 2 at. of oxygen, which the nitric acid has given off in the 

 formation of hyponitrous acid, and 4 at. of water, we obtain 

 the formula of alloxan, for 



2U1(= C N,, OJ+4HO + 2 O = C H N,0,. 



Parabanic acid is obtained by treating one part of uric acid, 

 or one part of alloxan in eight parts of nitric acid, evaporating 

 to the consistence of a syrup, and allowing it to stand for some 

 time, when it yields colouiiess crystals which may be purified 

 by recrystallization. Its formula is C^ N, 0^ + 2110. 



It is formed by the action of hyponitrous acid on the urea 

 of the uric acid ; the 2 at. of uril take up 4 at. of oxygen, and 

 2 at. of water, and yield 2 at. of carbonic acid, and 1 at. of 

 hydrated parabanic acid : thus 



2Ul + 2HO + 40=2CO.^ + (C, N^ 0^ + 2 HO.) 

 Or it may be regarded as produced by the action of oxygen on 

 alloxan, for 



Cs H, N, 0,, + 20 = 2CO., + 2HO + (C, N, 0, + 2H0.) 



Oxaluric acid is obtained by boiUng parabanic acid in a solu- 

 tion of ammonia. If the mixture be evaporated and allowed 

 to cool, crystals of oxalurate of ammonia wiU separate them- 

 selves. On the addition of an acid to a concentrated solution 

 of this salt, oxaluric acid is separated as a crystalline powder. 

 Its formula is C^ Hg N„ O. + HO. It is formed by the addi- 

 tion of 2 at. of water to the constituents of parabanic acid : it 

 contains further the elements of 2 at. of oxalic acid, and 1 at. 

 of urea, and by boiling in water is completely decomposed into 

 free oxalic acid, and oxalate of urea. 



Liebig observes that "when uiic acid is subjected to the 

 action of oxygen, it is first resolved into alloxan and urea ; a 

 new supply of oxygen acting on the alloxan causes it to resolve 

 itself either into oxalic acid and urea, or into oxaluric and 

 parabanic acids, or into carbonic acid and urea,'^ (Animal 

 Chemistry, p. 137.) The reactions which we have already 

 given are sufficient to explain this statement. We have 

 shown that — 



Uric acid = 2 Ul + urea, and alloxan ;= 2 Ul -|- Oj + 4 HO ; 

 consequently, 



Ui-ic acid 4- Oj -f 4 HO = alloxan + luea. 



