BILE ACIDS 325 



poured into a beaker and the small quantity of oily substance separated after 

 cooling. The crystals are filtered off, washed with 60 per cent, acetic acid 

 and water and dried at 100. The product melts at 170-175. A yield of 

 32 gm. melting at 172-173 and 42 gm. melting at 170 was obtained from 

 4 litres of bile. 



Deoxycholic acid can be prepared in a similar way from commercial 

 sodium taurocholate by boiling 500 gm. with 3 litres of water and 200 gm. of 

 caustic soda. A yield of 25 gm. melting at 173-174 results. 



Cholic acid is prepared from the mother liquors by distilling off the acetic 

 acid in vacua, treating the residue with hot alcohol and making alkaline to 

 phenolphthalein with caustic soda ; the alcohol is evaporated, the sodium salts 

 dissolved in water and the cholic acid precipitated with hydrochloric acid. 

 The fluid crystalline mass is squeezed to remove mother liquor and digested 

 with hot water to remove acetic acid. A hard cake smelling of acetic acid 

 results on cooling; it is broken up, powdered, dried in vacua over caustic 

 soda and subsequently at 100. It is recrystallised from 2 volumes of ab- 

 solute alcohol. 50 gm. of cholic acid and 7 gm. of fatty acid were obtained 

 from 4 litres of bile. Schryver's method gives a bigger yield of cholic acid. 



Properties of Cholalic Acid. 



Cholalic acid is soluble in water, i part in 4000 cold, i part in 750 hot ; it 

 is more soluble in alcohol, i part in 20. It dissolves in alkalies and in alkaline 

 carbonates with evolution of carbon dioxide. It crystallises from dilute aqueous 

 solutions or from dilute acetic acid in tetrahedra containing i molecule of water 

 and from alcohol containing i molecule of alcohol, which is given off at 130. 

 It has a sweet-bitter taste and the anhydrous substance melts at 195. 



Cholalic acid is dextrorotatory. 



It gives off aromatic vapours when heated and is stable to alkali. The 

 alkaline salts are easily soluble in water, less so in alcohol ; they crystallise 

 on evaporating the alcoholic solution or on precipitating it with ether. The 

 lead and barium salts are precipitated on adding lead acetate or barium chloride 

 to a not too dilute solution. The barium salt crystallises in glistening needles 

 arranged in rosettes and is easily soluble in alcohol and hot water. 



On heating* to high temperatures or with dehydrating agents, e.g. glacial 

 acetic acid, it is converted into anhydrides dyslysin, choloidic acid 

 which are not crystalline and are reconverted into cholalic acid by boiling 

 with alcoholic potash. On oxidation cholalic acid is converted into dehydro- 

 cholalic acid, bilianic acid, isobilianic acid. Another acid, cholicamphoric 

 acid, C l0 H l6 O 4 , has also been obtained. It is not easily reduced, but an acid, 

 cholylic acid, C 24 H 4 oO 2 , has been obtained. 



Reactions and Tests of Cholalic Acid. 



(1) The crystalline form, dextrorotation and the formation of aromatic 

 substances on heating are an indication of the presence of cholalic acid. 



(2) Mylius' Reaction. If '0-2 gm. of cholalic acid be dissolved in 0-5 gm. 

 of alcohol and i c.c. of *iN iodine solution be added and the solution 

 gradually diluted with water, the brown liquid sets to a mass of microscopic 

 needles with a metallic lustre and blue appearance. 



(3) Cholalic acid dissolves in concentrated sulphuric acid, giving a reddish 

 yellow solution with a green fluorescence. 



(4) Pettenkofers Reaction. On adding concentrated sulphuric acid drop 

 by drop to an aqueous solution of cholalic acid in which a tiny crystal of cane 

 sugar has been dissolved and keeping the temperature below 70, the cholalic 



