UREA. HIPPURIC ACID. AMINOACIDS 



The fact that hippuric acid is exceedingly unstable, being 

 readily dissociated by evaporating the urine in weak alkaline 

 reaction by heat, or by urinary fermentation, has led to the 

 introduction of an increasing number of methods in which 

 the hippuric acid is estimated as benzoic acid. The latter 

 compound because of its stability and ready solubility in 

 ether and other solvents offers certain advantages. 45 The 

 method of Wiechowski 46 is exact but time consuming, the 

 benzoic acid being separated by aqueous distillation. 

 Steenbock 47 oxidizes the alkalinized urine with peroxide of 

 hydrogen, separates the phenols with bromine water after 

 acidulation, and removes the benzoic acid by shaking with 

 ether; after evaporation of the ether the benzoic acid is 

 sublimed in a special glass apparatus and weighed. Folin 48 

 oxidizes the urine with nitric acid, extracts with chloroform, 

 washes the chloroform solution with a saturated salt solu- 

 tion containing hydrochloric acid and determines the benzoic 

 acid by titration with alcoholic sodium hydrate solution. 



Eecently one of the author's pupil's, Hryntschak, 49 has 

 elaborated what is apparently a very satisfactory method. 

 The urine is oxidized after treatment with boiling sodium 

 hydrate solution by an excess of potassium permanganate ; 

 the manganese which separates is dissolved by sodium bisul- 

 phite and sulphuric acid ; and the clear colorless fluid then 

 extracted with ether. After evaporation of the ether the 

 benzoic acid is taken up with chloroform, and finally in 

 pure, crystallized form is weighed. Control determinations 

 of hippuric acid in known solutions show that the method is, 



46 R. Cohn, Th. Pf eiffer, C. Bloch, R. Riecke, W. Wiechowski. Literature 

 upon the Estimation of Hippuric Acid : Th. Hryntschak, Biochem. Zeitschr., 1$, 

 316, 1912. Conducted under direction of 0. v. Fiirth. 



W. Wiechowski, Hofmeister's Beitr., 7, 262, 1906. 



"H. Steenbock (Univ. of Wisconsin), Jour, of Biol. Chem., 11, 201, 1912. 



44 O. Folin and F. F. Flanders (Harvard Med. School, Boston), Jour, of 

 Biol. Chem., 11, 257, 1912. 



1. c. 



