412 PHYSIOLOGICAL CHEMISTRY 



is another important oxyacid sometimes present in the urine. Under 

 the name glycosuric acid it was first isolated from the urine by Prof. 

 John Marshal] of the University of Pennsylvania; subsequently Bau- 

 mann isolated it and determined its chemical constitution. It occurs in 

 cases of alcaptonuria. A urine containing this oxyacid turns greenish- 

 brown from the surface downward when treated with a little sodium 

 hydroxide or ammonia. If the solution be stirred the color very soon 

 becomes dark brown or even black. Homogentisic acid reduces 

 alkaline copper solutions but not alkaline bismuth solutions. Uro- 

 leucic acid is similar in its reaction to homogentisic acid. 



Hydroxymandelic Acid or parahydroxyphenyl-glycolic acid, 



OH 



CH(OH).COOH, 



has been detected in the urine in cases of yellow atrophy of the liver. 

 Kynurenic Acid or 7-hydroxy-]8-quinoline carboxylic acid, 



CHCOH 



HC C C.COOH, 



I II I 

 HC C CH 



\/\/ 

 CHN 



is present in the urine of the dog and has recently been detected by 

 Swain in the urine of the coyote. To isolate it from the urine proceed 

 as follows: Acidify the urine with hydrochloric acid in the proportion 

 1:25. From this acid fluid both the uric acid and the kynurenic acid 

 separate in the course of 24-48 hours. Filter off the combined crys- 

 talline deposit of the two acids, dissolve the kynurenic acid in dilute 

 ammonia (uric acid is insoluble), and reprecipitate it with hydrochloric 

 acid. If a solution containing kynurenic acid be evaporated to dryness 

 with hydrochloric acid and potassium chlorate, a reddish residue is 

 obtained which becomes first brownish green and then emerald green on 

 adding ammonia (Jaffe). 



Kynurenic acid may be quantitatively determined by Capaldi's 

 method. 1 



COOH. 



BENZOIC ACID, 



'.'.." " . N V - " t 



1 Zeitschrift fiir physiologische Chemie, 23, 92, 1897. 



