80 THE NITROGENOUS DERIVATIVES OF THE ALBUMINS. 



we find that all of them contain the group HCN. Adenin, indeed, 

 is a polymeric compound of hydrocyanic acid, and xanlhin can be 

 obtained by direct hydration of the same body (Gautier). On heat- 

 ing with alkalies or with water the nucleinic bases generally do not 

 give rise to the formation of urea, and they cannot hence be re- 

 garded as ureids, although a close relationship exists between them. 

 By a simultaneous process of oxidation and hydration guanin thus 

 gives rise to parabanic acid, and it is possible indeed to pass fnmi 

 guanin to xanthin and hypoxanthin by a series of simple reactions 

 without the intervention of urea. These changes are represented by 

 the equations : 



NH 2 CO NH X 



+ | >CO -f CO 2 



uanin. NH 2 CO NH/ 



Guanidin. I'arabanic acid. 



HNO 2 = C 5 H 4 N 4 2 + 2N + H 2 O. 

 Guann. Xanthin. 



C 5 H 4 N 4 2 + 2H = C 5 H 4 N 4 -f H. 2 O. 



Xanthin. Hypoxanthin. 



Xanthin, however, on oxidation and hydration yields urea and 

 alloxan, which latter is further oxidized to parabanic acid and 

 carbon dioxide, as shown in the equations : 



CO-NH X 



C 5 H 4 N 4 O 2 -t- 2O + H 2 O = CO >CO + CO< 

 Xanthin. | \NH 2 



CO NH/ Urea. 



Alloxan. 



CO NH X 



\ CO NH X 



CO >CO-fO=| >CO + CO 2 



/ CO-NH/ 



)_ NH / 



Alloxan. Parabanic acid. 



CO 



The close relationship which exists between uric acid and the nucle- 

 inic bases thus becomes apparent, as uric acid on oxidation and 

 hydration gives rise to the same products as xanthin : 



C 5 H 4 N 4 3 + O + H 2 = C 4 H 2 N 2 4 + CON 2 H 4 . 

 Uric acid. Alloxan. Urea. 



This relationship is further shown by decomposing the primary 

 xanthin bases and uric acid with fuming hydrochloric acid or 

 hydriodic acid under high pressure. Qualitatively the same prod- 

 ucts are thus obtained, viz., ammonia, carbon dioxide, glycocoll, 

 and formic acid, while the quantitative relations, of course, vary 

 with the nature of the individual substance. 



C 5 H 5 N 5 -f- 8H 2 O = 4NH 3 -f CO 2 4- CH 2 .NH 2 COOH + 2H.COOH. 

 Adeiiin. Glycocoll. Formic acid. 



C 5 H 4 N 4 -f 7H 2 O = 3NH, -f CO 2 + CH 2 .NH 2 .COOH + 2H.COOH. 

 Hypoxanthin. 



