BILE ACIDS 329 



(fr) From Dogs Bile. 



Dog's bile is treated with alcbhol to remove mucin and the alcoholic 

 filtrate is evaporated to dryness. The residue is dissolved in absolute 

 alcohol and carefully treated with ether. The precipitate is pressed out and 

 dissolved in water. The solution is fractionally precipitated with ferric 

 chloride, the reaction being kept neutral by adding sodium carbonate, and 

 diluted with water. This is continued so long as the precipitates on decom- 

 posing with sodium carbonate give a solution having a bitter taste. Tauro- 

 choleic acid is obtained from the precipitate. The nitrate is neutralised, 

 and evaporated ; the residue is then extracted with alcohol : evaporation and 

 extraction are repeated several times. The free acid is obtained from the 

 salt as described under cod's bile. 



Properties. 



Taurocholic acid is easily soluble in water, the amorphous form more 

 easily than the crystalline. It dissolves easily in alcohol, but is insoluble in 

 ether, benzene, chloroform. It has a sweet, very slightly bitter, taste and 

 is dextrorotatory. It yields taurine and cholalic acid on hydrolysis. 



The amorphous form separates on adding ether to the alcoholic solution ; 

 the crystalline form on adding ether to the alcoholic solution containing 

 a drop of water. The crystals contain i molecule of water. Taurocholic 

 acid on heating turns yellow or brown at 100, sinters at 140, begins to de- 

 compose at 1 60 and melts at 180 to a brown liquid. 



The sodium salt is soluble in water, less so in cold alcohol ; from hot 

 alcohol it separates in large flakes if the solution does not set as a jelly. It 

 can be obtained as crystals by adding ether to the alcoholic solution. 



The sodium salt is not precipitated by lead acetate or ferric chloride. 



It resembles the other bile acids in giving the fluorescent and Pettenkofer's 

 reactions, but is distinguished by its taste, solubility and sulphur content. 



Taurocholeic Acid. 



Taurocholeic acid accompanies taurocholic acid in dog's bile. 



The precipitates obtained in the preparation of taurocholic acid with ferric 

 chloride and sodium carbopate are decomposed with sodium carbonate ; the 

 filtrate is evaporated and the residue extracted with hot alcohol. The 

 alcoholic solution is evaporated and extracted with cold alcohol. Extraction 

 and evaporation are repeated until a clear solution results. The acid is 

 obtained by treating this solution with alcohol containing hydrochloric acid, 

 the sodium chloride is filtered off and the solution precipitated with ether. 



Taurocholeic acid is readily soluble in alcohol, but insoluble in ether, 

 chloroform and benzene. It is amorphous and deliquescent and has a bitter 

 taste. 



