350 PHYSIOLOGICAL CHEMISTRY. 



The preparation of creatinin zinc chloride on a large scale from 

 urine is done in the same way. The creatinin is obtained from 

 the creatinin zinc chloride by boiling with lead hydroxide, filtering, 

 decolorizing the filtrate with animal charcoal, evaporating, treating 

 the residue with strong alcohol (which leaves the creatin undis- 

 solved), evaporating to crystallization, redissolving in water, and 

 recrystallizing. 



Xanthocreatinin. This body, which has been spoken of in a previous chap- 

 ter on the muscles, has been found in dog's urine after the injection of crea- 

 tinin into the abdominal cavity (MoNAKi), and in human urine after several 

 hours of continuous marching. The correctness of these observations is 

 disputed by STADTHAGEN. 



Uric Acid, Ur, CsH^Os. The structural formula of this acid, 



according to MEDICUS, is CO/ C.NH/CO, and this acid 



\NH.CO 



may therefore be considered, from its constitution as a derivate of 

 acrylic acid, as acrylic acid diureid. 



Uric acid has been synthetically prepared by HORBACZEWSKI in 

 several ways. On fusing urea and glycocoll, uric acid is formed 

 according to the formula 3CON 2 H 4 + C 2 H 6 N0 2 = C 6 H,N~A + 

 2H 2 + 3NH 3 , and in this reaction hydantoin and biuret are formed 

 as intermediate products. On melting methylhydantoin with urea 

 or methylhydantoin with biuret or with allophanic-acid amyl-ester 

 HORBACZEWSKI obtained methyl-uric acid. He also obtained uric 

 acid on heating trichlor-lactic acid, or still better trichlor-lactic acid- 

 amid, with an excess of urea. If we eliminate from the reaction 

 the numerous by-products (cyanuric acid, carbon dioxide, etc.), 

 then this process may be expressed by the formula CsClgH^OaN -f- 

 2CON 2 H, = C.H 4 N 4 0, + H 2 + NH 4 C1 -f 2-H01. 



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 a splitting and oxidation takes 

 place, and either monoureid or diureid is produced. By oxidation 

 with lead peroxide, CARBON DIOXIDE, OXALIC ACID, UREA, and 

 ALLANTOIN, which last is glyoxyl diureid, are produced (see below). 

 By oxidation with nitric acid in the cold UREA and a monoureid, the 



