GLYCOCHOLIC ACID. 419 



This extremely delicate test fails, however, when the solution is 

 heated too high, or if an improper quantity generally too much of 

 the sugar is added. In the last-mentioned case the sugar easily car- 

 bonizes and the test becomes brown or dark brown. The reaction fails 

 if the sulphuric acid contains sulphurous acid or the lower oxides of 

 nitrogen. Many other substances, such as proteins, oleic acid, amyl 

 alcohol, and morphine, give a similar reaction, and therefore in doubt- 

 ful cases the spectroscopic examination of the red solution must not be 

 forgotten. 



PETTENKOFER'S test for the bile-acids depends essentially on the 

 fact that furfurol is formed from the sugar by the sulphuric acid (MYLIUS). 

 According to MYLIUS and v. UDRANSZKY 1 a 1 p. m. solution of furfurol 

 should be used. Dissolve the bile, which must first be decolorized by 

 animal charcoal, in alcohol. To each cubic centimeter of alcoholic 

 solution of bile in a test-tube add 1 drop of the furfurol solution and 

 1 cc. concentrated sulphuric acid, and cool when necessary, so that the 

 test does not become too warm. This reaction, when performed as 

 described, will detect ^r to j^- milligram cholic acid (v. UDRANSZKY). 

 Other modifications of PETTENKOFER'S test have been proposed. 



The reaction with furfurol is not identical with that obtained with 

 cane-sugar, according to VILLE and DERRIEN, and the absorption-bands 

 do not occur in the same place in the two cases. The reaction with cane- 

 sugar does not depend, according to these investigators, upon a furfurol 

 formation from the sugar. The acid hydrolyzes the sugar, and from the 

 fructose produced, 4-methyl-2-oxyfurfurol is formed by the further action 

 of the acid, and this gives the color reaction with the cholic acid. Instead 

 of furfurol other aldehydes such as vanillin and anisaldehyde can be 

 used according to VILLE and DERRIEN. 2 



Glycocholic Acid. The constitution of the glycocholic acid occurring 

 in human and ox-bile, and which has been most studied, is represented 

 by the formula C26H43NOe. Glycocholic acid is absent, or nearly so, 

 in the bile of carnivora. On boiling with acids or alkalies this acid, 

 which is analogous to hippuric acid, is converted into cholic acid and 

 glycocoll. 



By the action of hydrazine hydrate upon the ethyl ester of cholic acid 

 BONDI and MULLER 3 prepared first cholic-acid hydrazide, and then, by 

 the action of nitrous acid upon this, they obtained the cholic-acid azide, 

 C23H3Q03CO.N3, and finally from this last in alkaline solution with glyco- 



1 Mylius, Zeitschr. f. physiol. Chem., 11; v. Udranszky, ibid., 12. 



2 Ville and Derrien, Chem. Centralbl. 1909, 2, 1699 and Compt. rend, soc., biol. 64 

 and 66. 



3 Zeitschr. f. physiol. Chem., 47. 



