GLYCOCHOLIC ACID. 397 



the course of a day. This red liquid shows a spectrum with two absorp- 

 tion-bands, the one at F and the other between D and E, near E. 



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 doubtful 

 cases the spectroscopic examination of the red solution must not be 

 forgotten. 



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

 tact that furfurol is formed from the sugar by the sulphuric acid, and 

 this body can therefore be substituted for the sugar in this test (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 -^ to -fa milligram cholic acid (v. UDRANSZKY). 

 Other modifications of PETTENKOFER'S test have been proposed. 



The assumption that PETTENKOFER'S reaction is due to the production* of 

 furfurol from the sugar is not sufficiently proven, and according to certain investi- 

 gators, such as BARDACHZI and VILLE 2 the spectrum is somewhat different 

 when using furfurol. 



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 C 2 6H 43 NO 6 . 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 BOND: and MULLER S prepared first cholic-acid hydrazide, and then, 

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

 azide, C23H 3 9O 3 CO.N3, and finally from this last in alkaline solution 

 with glycocoll they synthetically prepared the alkali salt of glycocholic 

 acid, at the same time splitting off nitrogen. 



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



Bardachzi, Zeitschr, f. physiol. Chem., 48; Ville, cited from Chem. Centralbl., 

 1907, 2, p. 1712 



Zeitschr f. physiol. Chem., 47. 



