CHEMISTRY OF THE LIVER. 321 



C 23 H 40 O 4 , and lithofellic acid, C 20 H 36 O 4 , are found in some 

 kinds of bile. 



Taurocholic Acid. To this substance the empirical form- 

 ula C 26 H 45 NSO 7 is given. \Yith weak acids it undergoes 

 likewise a hydrolytic cleavage from which taurin and cholalic 

 acid result. Taurin appears to be aminoethylsulphonic acid, 

 C 2 H 4 NH 2 'HSO 3 , and the cleavage would be represented in 



this way : 



C M HNS07 + H 2 = CH.0. + C 2 H 4 NH 2 HSO 3 . 



The free acid has a bitter-sweet taste; it is much more soluble 

 in water than the glycocholic acid and somewhat soluble in 

 alcohol. The free acid has the property of holding glyco- 

 cholic acid in aqueous solution, which is shown by the diffi- 

 culty in precipitating the mixed acids from ox bile. The free 

 acid is but slightly soluble in ether. The alkali salts are solu- 

 ble in water and alcohol. 



Preparation of Acids from Ox Bile. This may be illustrated by the fol- 

 lowing. Evaporate 200 to 300 cc. of the bile to dryness, or as near to 

 dryness as possible, on the water-bath with .the addition of about 60 grams 

 of bone-black. After cooling the mass rub it up thoroughly, transfer to 

 a flask and extract with alcohol by heating over a water-bath. The two 

 bile salts are soluble in the alcohol, while the mucin and inorganic salts 

 present are not. Therefore cool the extracted mixture and filter. The 

 filtrate contains the bile salts along with cholesterol, some fat and traces 

 of other substances. There is also some water present Evaporate the 

 filtrate to dryness, take up with absolute alcohol and filter again. Taking 

 advantage of the practical insolubility of the bile salts in ether they may 

 "be precipitated in this way : Add to the strong alcoholic solution an excess 

 of dry ether, or enough to cloud the mixture, and allow to stand. After 

 some hours or days a crystalline precipitate of the bile salts separates. 

 The crystals may be used for preparation of other substances, or for tests. 

 In the mother liquor cholesterol may be detected by the tests given in an 

 earlier part of this work. 



Preparation of Glycocholic Acid. Use the larger part of the above 

 described crystalline precipitate for this purpose. Dissolve in water and 

 add enough dilute sulphuric acid to produce a marked turbidity. Add a 

 little ether, shake the mixture well and allow to stand in a cold place. 

 The glycocholic acid separates in the form of fine silky needles. Press 

 out the mother liquor, redissolve in hot water and allow to crystallize a 

 second time. A nearly pure product may be so obtained. 



Preparation of Taurocholic Acid. The separation of this acid from the 



