664 URINE. 



acid (E. FISCHER and TULLNER) and finally E. FISCHER and ACH * have 

 prepared uric acid fiom pseud ouric acid by heating with oxalic acid to 

 145 C. 



On strongly heating uric acid it decomposes with the formation of 

 urea, hydrocyanic acid, cyanuric acid, and ammonia. On heating with 

 concentrated hydrochloric acid in sealed tubes to 170 C. it splits into 

 glycocoll, carbon dioxide, and ammonia. By the action of oxidizing 

 agents splitting and oxidation take place, and either monoureides or 

 diureides are produced. By oxidation with lead peroxide, carbon dioxide, 

 oxalic acid, urea, and allantoin, which last is glyoxyldiureide, are pro- 

 duced (see below). By oxidation with nitric acid in the cold, urea and 

 amonoureide, the mesoxalyl urea, or alloxan, are obtained, C 5 H 4 N 4 O 3 + 

 O + H 2 O==C 4 H 2 N 2 4 + (NH 2 )2CO. On warming with nitric acid, alloxan 

 yields carbon dioxide and oxalyl urea, or parabanic acid, C 3 H 2 N 2 O 3 . 

 By the addition of water the parabanic acid passes into oxaluric acid, 

 C3H 4 N2O4, traces of which are found in the urine and which easily splits 

 into oxalic acid and urea. In alkaline solution uric acid may, by taking 

 up water and oxygen, be transformed into a new acid, uroxanic acid, 

 C 5 H 8 N 4 O 6 , which may then be changed into oxonic acid, C 4 H 5 N 3 O 4 . 2 

 Uric acid may, as F. and L. SESTINI as well as GERARD have shown, 

 undergo bacterial fermentation with the formation of urea. According 

 to ULPIANI and CiNGOLANi, 3 uiic acid is quantitatively split into urea 

 and carbon dioxide, according to the equation 



G 5 H 4 N 4 O 3 + 2H 2 O + 30 = 3C0 2 + 2CO (NH 2 ) 2 . 



Uric acid occurs most abundantly in the urine of birds and of scaly 

 amphibians, in which animals the greater part of the nitrogen of the urine 

 appears in this form. Uric acid frequently occurs in the urine of carniv- 

 orous mammalia, but is sometimes absent; in urine of herbivora it is 

 habitually present, though only as traces; in human urine it occurs in 

 greater but still small and variable amounts. Traces of uric acid are 

 also found in several organs and tissues, as in the spleen, lungs, heart, 

 pancreas, liver (especially in birds), and in the brain. It always occurs 

 in the blood of birds. Traces have been found in human blood under 

 normal conditions. Under pathological conditions it occurs to an 

 increased extent in the blood, as in pneumonia and nephritis, but espe- 

 cially in leucaemia and sometimes also in arthritis. Uric acid also occurs 



1 Horbaczewski, Monatshefte f. Chem., 6 and 8; Behrend and Roosen, Ber. d. d. 

 chem. Gesellsch., 21; Fischer and Tullner, ibid., 35; Fischer and Ach, ibid., 28. 



2 See Sundwik, Zeitschr. f . physiol. Chem., 20 and 41; also Behrend, Annal. d. Chem. 

 u. Pharm., 333. 



3 See Chem. Centralbl., 1903, where the other investigators are cited, and Centralbl. 

 f. Physiol., 19. 



