106 THE CLEAVAGE PRODUCTS OF THE NUCLEOPROTEIDS. 



posed into urea and dialuric acid, which latter further yields urea 

 and tartronic acid. In this manner the character of uric acid as a 

 diureid of the first order is demonstrated. The reactions which 

 take place are represented by the equations : 



(1) C 5 H 4 N40 3 + 2H 2 =- C 4 H 4 N 2 4 + CO(NH 2 ) 2 



Uric acid. Dialuric acid. Urea. 



(2) C 4 H 4 N 2 4 + 2H 2 = C 3 H 4 5 + CO(NH 2 ) 2 

 Dialuric acid. Tartronic acid. Urea. 



On treating with an oxidizing agent, in the presence of water, uric 

 acid is similarly decomposed into urea and the mono-ureid alloxan, 

 which can be further decomposed into urea and mesoxalic acid : 



(1) aH 4 N 4 3 + H 2 + O = C 4 H 2 N 2 4 + CO(NH 2 ) 2 

 Uric acid. Alloxan. 



(2) C 4 H 2 N 2 O 4 + 2H 2 = C 3 H 2 O ? + CO(NH 2 ) 2 



Alloxan. Mesoxalic 



acid. 



Its relation to the di-ureids of the second order is shown by oxidiz- 

 ing the substance with peroxide of manganese in neutral solution at 

 a moderate temperature. In this manner allantoin is formed, from 

 which, on further oxidation, urea and oxalic acid result : 



(1) C5H.NA + H20 + O = C 4 H 6 N 4 3 + CO 2 



Allantoin. 



(2) C 4 H 6 N 4 3 -f 2H 2 O + O = C 2 H 2 O 4 + 2CO(NH 2 ) 2 



Oxalic 

 acid. 



Of special interest, further, is the formation of murexid, or 

 ammonium purpurate, which results when uric acid, even in minimal 

 amounts, is evaporated together with nitric acid, and the reddish 

 residue is brought in contact with ammonia. A beautiful purplish- 

 red color then develops, which is characteristic of uric acid and its 

 salts (murexid test). The reactions which take place may be rep- 

 resented by the equations : 



(1) C 5 H 4 N 4 O 3 -f 2H 2 O = C 4 H 4 N 2 O 4 -f CO(NH 2 ) 2 



Dialuric acid. 



(2) C 4 H 4 N 2 O 4 + NH 4 OH -= C 4 H 3 (NH 4 )N 2 O 4 + H 2 O 



Ammonium 

 dialurate. 



(3) 2C 4 H 3 (NH 4 )N 2 4 + O = C 8 H 4 (NH 4 )N 5 O 6 + 3H 2 O 

 Ammonium dialurate. Murexid. 



The relation of uric acid to the mono-ureids of the second order, 

 finally, is shown by treating one part of uric acid with three parts 

 of nitric acid (50 per cent, solution), and heating to 70 C. On sub- 

 sequent evaporation to a syrup and cooling, parabanic acid crystal- 

 lizes out, and on decomposition yields urea and oxalic acid : 



(1) C 5 H 4 NA + H 2 + O = C 4 H 2 N 2 4 -f CO (NH 2 ) 2 



Alloxan. 



.(2) C 4 H 2 N 2 4 + O = C 3 H 2 N 2 3 + CO 2 



Parabanic 

 acid. 



(3) C 3 H 2 N 2 3 + 2H 2 =C,HA + CO(NH 2 ) 2 



Oxalic acid. 



