388 PHYSIOLOGICAL CHEMISTRY 



CH 



/\ 



HC C C.OH 





20 



HC C CH 



CH NH 



Indoxyl, 



CH CH 



/\ /\ 



HC C---C.O O.C C CH 



|| | +2H 2 



HC C C -C C CH 



CH NH NH CH 



Indigo-blue, 



2. Obermayer's Test. Nearly fill a test-tube with a mixture composed of 

 equal volumes of Obermayer's reagent 1 and the urine under examination. 

 Add 2-3 c.c. of chloroform, place the thumb over the end of the test-tube and 

 shake thoroughly. How does this compare with Jaffe's test? 



3. Jolles' Reaction. 2 To 10 c.c. of urine add i c.c. of a 5 per cent alcoholic 

 thymol solution and shake. Add about 10 c.c. of fuming HC1 containing 5 

 grams of ferric chloride per liter. Shake again carefully and let stand for 15 

 minutes. Add about 4 c.c. of chloroform and extract the pigment by repeated 

 gentle shaking. The chloroform becomes intensely violet. 0.0032 mg. of indi- 

 can can be detected in 10 c.c. of urine. It is much the most delicate test for 

 indican. 



CO.NH.CH 2 .COOH. 

 HIPPURIC ACID, 



This acid occurs normally in the urine of both the carnivora and 

 herbivora but is much more abundant in the urine of the latter. It is 

 formed by a synthesis of benzoic acid and glycocoll which takes place 

 in the kidneys and elsewhere 3 . The glycocoll comes from decomposi- 

 tion of protein. The benzoic acid thus utilized may come from (i) pre- 

 formed benzoic acid of fruits and vegetables; (2) other aromatic com- 

 pounds of fruits and vegetables; (3) aromatic ammo-acids (tyrosine 

 and phenylalanine) from the alimentary tract. The average excretion 

 of hippuric acid by an adult man for 24 hours under normal conditions 

 is about 0.7 gram. Hippuric acid crystallizes in needles or rhombic 

 prisms (see Fig. 125, p. 389) the particular form depending upon the 



1 Obermayer's reagent is prepared by adding 2-4 grams of ferric chloride to a liter of con- 

 centrated HC1 (sp. gr. 1.19). 



2 Zeit. physiol. Ckem., 94, 79, 1915. 



3 Kingsbury and Bell: Jour. Biol. Chem., 21, 297, 1915. 



