THE U REIDS. 105 



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 



COG 1 



-NH X 



I II /CO. 



HN-C-NH/ 



It is thus 2.6.8 trioxypurin. It was first obtained synthetically 

 by heating a mixture of glycocoll and urea at a temperature of 

 220 to 230 C. The reaction 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 + 3NH 3 

 Glycocoll. Urea. Uric acid. 



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

 trichlorolactic amide : 



C 3 C1 3 2 H 2 .NH 2 + 2CO(NH 2 ) 2 = C 5 H 4 N 4 O 3 + H 2 O -f 2HC1 -f 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 



OC C(OH)+ CO(NH 2 ) 2 = CO C NH X 

 | || | || >CO + 2H 2 



HN C(OH) HN C NH/ 



When heated 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 

 sodium amalgam uric acid is first transformed into xanthin, and sub- 

 sequently into hypoxanthin. The close relationship which exists 

 between the nucleinic bases and uric acid is thus further shown 

 (see page 104). 



Analogous to the synthetic formation of uric acid from urea and 

 glycocoll, we find that on decomposition with hydriodic acid the 

 substance yields carbon dioxide, ammonia, and glycocoll, viz., the 

 same products which are obtained from the nucleinic bases. 



From the reactions which have thus far been described the nature 

 of uric acid as a ureid is not apparent. If the hydrolytic decom- 

 position of the substance is effected less energetically, this becomes 

 manifest at once. On prolonged boiling with water it is decom- 



