BILE ACIDS 



(3) ttammarsteris Method. 



Ox bile is evaporated to a syrup, the syrup extracted with alcohol and 

 the alcoholic extract evaporated. The residue is dissolved in water and pre- 

 cipitated with lead acetate. The precipitate is decomposed by boiling with 

 sodium carbonate, the solution evaporated to dryness and extracted with 

 alcohol. The alcoholic solution is evaporated, the residue is dissolved in 

 water and boiled with charcoal to decolorise. The solution is mixed with 

 ether and precipitated with hydrochloric acid according to Hiifner's method. 

 The crystals are washed free from hydrochloric acid. 



The mixture of acids contained in this precipitate is separated as follows : 



Glycocholic acid is separated by boiling out the precipitate with water ; it 

 separates out on cooling and is recrystallised from water. 



The residue is dissolved in very dilute alkali and the neutral solution 

 treated with barium chloride. The sticky mass of barium salts is dissolved 

 in boiling water and treated with sodium carbonate. The filtrate is evaporated 

 and extracted with alcohol. The alcoholic extract is evaporated, the residue 

 dissolved in water, the solution decolorised by boiling with charcoal and 

 precipitated in dilute solution with hydrochloric acid and ether as above. 

 The glycocholeic acid is precipitated and is purified by repeating the process. 



Properties. 



Glycocholic acid crystallises in needles (Fig. 53) which are soluble with 

 difficulty in cold water (i part in 300), 

 more easily in hot water (i part in 120), 

 very easily soluble in alcohol and in 

 alkalies, almost insoluble in ether. The 

 alcoholic solution on the addition of 

 water becomes turbid and deposits 

 crystals. The alkaline solution is pre- 

 cipitated by acids. On heating in a 

 capillary tube, glycocholic acid softens 

 at 133 and melts at 152. It has a 

 sweet-bitter taste and is dextrorotatory. 

 The alkaline salts are obtained by 

 evaporation of the alcoholic solution ; 

 they dissolve fats and cholesterol and 

 give precipitates with lead acetate, ferric 

 chloride, silver nitrate. The lead salt 

 is soluble in hot alcohol and separates 

 as a powder on cooling. The barium FIG. 53- ^Glycocholic acid. (After Funke. 



salt is easily soluble in water. 



On boiling with water, glycocholic acid changes into paraglycocholic acid 

 which crystallises in platelets melting at 183-188. It is reconverted into 

 glycocholic acid by crystallisation from alcohol. 



It dissolves in concentrated sulphuric acid and on warming cholonic 

 acid, C 2 <jH 45 O 5 N, separates out. This substance is also formed by boiling 

 glycocholic acid with concentrated hydrochloric acid. Its barium salt is 

 insoluble in water. 



Glycocholic acid is distinguished by its solubility, taste and rotation. It 

 gives the fluorescent reaction and Pettenkofer's reaction, but not Mylius' 

 reaction described under cholalic acid. 



