148 PHYSIOLOGICAL CHEMISTRY. 



Taurocholic acid may be obtained, though only with difficulty, 

 in fine needles which deliquesce in the air (PARKE). It is very 

 soluble in water, and can hold the difficultly-soluble glycocholic 

 acid in solution. This is the reason why a mixture of glycocholate 

 with a sufficient quantity of taurocholate, which often occurs in ox- 

 bile, is not precipitated by a dilute acid. Taurocholic acid is readily 

 soluble in alcohol but insoluble in ether. Its solutions have a bitter- 

 sweet taste. Its salts are, as a rule, readily soluble in water, and 

 the solutions of the alkali salts are not precipitated by copper sul- 

 phate, silver nitrate, or sugar of lead. Basic lead acetate gives, on 

 the contrary, a precipitate which is soluble in boiling alcohol. 



Taurocholic acid is best prepared from decolorized, crystallized 

 dog-bile, which contains only taurocholate. The solution of this 

 bile is precipitated by basic lead acetate and ammonia, and the 

 washed precipitate dissolved in boiling alcohol. The filtrate is now 

 treated with H 2 S, and this filtrate is evaporated at a gentle heat to 

 a small volume, and treated with an excess of water-free ether. 

 The acid sometimes partially crystallizes. 



Cheno-taurocholic Acid. This is the most essential acid of goose-bile 

 and has the formula CagH^gNSOe. This acid, though little studied, is known 

 to be amorphous and soluble in water and alcohol. 



As repeatedly mentioned above, the two bile-acids split on 

 boiling with acids or alkalies into non-nitrogenized cholalic acid 

 and glycocoll or taurin. Therefore we will now describe the prod- 

 ucts of this splitting. 



Cholalic Acid. The ordinary cholalic acid obtained as a decom- 

 position product of human and ox bile, which occurs regularly in 

 the contents of the intestines and in the urine in icterus, and 

 which is identical with DEMAR9AY's cholic acid, has, according 

 to STRECKER and nearly all recent investigators, the constitution 

 C^H^Og ; but others give as the formula C^H^Os (LATSCHINOFF). 

 According to MYLIUS, cholalic acid is a monobasic alcohol-acid with 

 a secondary and two primary alcohol groups. Its formula may there- 



( CHOH 



fore be written C^H^ \ (CH 2 OH) 2 . On oxidation it first yields 

 (COOH 



deliydrocholalic acid (AUTHOR), and then bilianic acid (CLEVE). 

 The formulae of these acids (when we take C^ for the cholalic acid) 

 are C^H^Oa and C^H^Og. On reduction (in putrefaction) cholalic 

 acid may yield desoxy cholalic acid, C 24 H 40 4 (MYLIUS). 



