82 THE NITROGENOUS DERIVATIVES OF THE ALBUMINS. 



The mono-ureids comprise alloxan, alloxanic acid, dialuric acid, 

 barbituric acid or malonyl-urea and its derivatives, all of which can 

 be decomposed into urea and non-nitrogenous acids containing three 

 atoms of carbon. From these another series of mono-ureids is de- 

 rived, which also yield urea and non-nitrogenous acids ; but the 

 latter, in contradistinction to the first group, contain only two atoms 

 of carbon. These include parabanic acid, oxaluric acid, allanturic 

 acid, and hydantoin and its derivatives, viz., hydantoic acid or glyco- 

 luric acid, and methyl-hydantoin. The di-ureids are similarly 

 divided into two groups, the first of which comprises uric acid, 

 alloxantin, murexid or ammonium purpurate, and hydurilic acid ; 

 while the second is represented by allantoin, allantoic acid, and 

 allituric acid. 



The best known representative of the ureids is uric acid. From 

 it all others can be derived, and a description of its general proper- 

 ties and reactions may serve as an illustration of the entire class. 



Uric acid is a crystallizable dibasic acid of the formula C 5 H 4 N 4 O 3 . 

 Structurally it may be regarded as a purin derivative, and may be 

 represented by the formula : 



HN CO 

 CO <>-NH x 



! li >co. 



HN C NH/ 



It was first obtained synthetically by treating a mixture of glycocoll 

 and urea at a temperature of 230 C. until the melted mass assumed 

 a yellowish color and became turbid. The reaction which took place 

 may be represented by the equation : 



CH 2 .NH 2 .COOH + 3CO(NH 2 ) 2 = C 5 H 4 N 4 O 3 + 2H 2 O -f 3NH 3 

 Glycocoll. Urea. Uric acid. 



The same result may be reached by heating a mixture of urea and 

 trichlorolactic amide : 



C 3 H 4 C1 3 N0 2 + 2CO(NH 2 ) 2 s= C 5 H 4 N 4 O 3 + H 2 O + HC1 + NH 4 C1 

 Trichlorolactic amide. 



As indicated in the previous section, moreover, uric acid also results 

 through the condensation of isodialuric acid and urea, according to 

 the equation : 



HN CO HN-CO 



II II 



CO C + CO(NH 2 ) 2 = CO C NH, 



| || 2 



HN C(OH) HN-C-NH/ 



When treated in the dry state uric acid is decomposed into hydro- 

 cyanic acid, cyanuric acid, ammonium carbonate, ammonium cyanate, 

 biuret, etc. Fused with an excess of potassium hydrate, it similarly 

 yields ammonia, potassium carbonate, oxalate, cyanate, and cyanide. 



On reduction with nascent hydrogen, in the presence of water and 



