288 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



The formula proposed by Medicus was ultimately proved to be the 

 correct one by the synthesis of uric acid by Fischer. 



The previous syntheses of uric acid by Horbaczewski (i) by fusing 

 together glycocoll and urea, (2) by combining trichlorlactanrde with 

 urea : 



NH a CC1 8 H 2 N HN C HN\ 



I I | | II >co 



CO + CHOH + CO = OC C HN/ 



I I III 



NH 2 CO.NH 2 H 3 N HN CO 



did not definitely prove its constitution. The synthesis by Behrend 

 and Roosen from aceto-acetic acid and the following synthesis com- 

 menced by Baeyer and completed by Fischer proves the constitution 

 of uric acid : 



(1) Malonyl urea or barbituric acid is obtained by heating urea and 

 malonic acid with phosphorus oxychloride. 



(2) Nitrous acid converts malonyl urea into oximidomesoxalyl urea 

 or violuric acid. 



(3) Aminomalonyl urea or uramil is obtained by reducing violuric 

 acid. 



(4) Potassium cyanate converts uramil by rearrangement, as in 

 the formation of urea, into pseudo-uric acid. 



(5) Pseudo-uric acid loses water on heating with fused oxalic acid, 

 or boiling with hydrochloric acid, and is changed into uric acid. 

 COOH NH CO NH CO NH CO NH CO 



CH 2 ->CO CH,->CO C=NOH->CO CH.NH 2 -CO CH 



COOH NH-CO NH CO NH CO NH CO 



Malonic Barbituric Violuric Uramil. 

 acid. acid. acid. 



NH CO NH CO 



CO CH.NH.CO. NH 9 - CO C NH V 



i ii 



NH-CO 



co. 



NH/ 



Pseudo-uric Uric 



acid. acid. 



Preparation. 



(I) From Snakes' Excrement \ or Guano. 



5 to i gm. of snakes' excrement (or guano) is powdered, suspended 

 in 100 c.c. of water, heated nearly to boiling and dissolved by adding 

 dilute sodium hydroxide. The solution is heated until ammonia from 

 ammonium salts and urea is no longer evolved and filtered from 

 insoluble material (sand, etc.). Excess of dilute hydrochloric acid is 

 added to the filtrate. Uric acid is precipitated ; it is filtered off when 

 the solution h is cooled and washed free from acid with water. The 

 product is generally almost pure, but may be purified by dissolving 



