324 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



cholic acids filtered off, washed, converted as before into their sodium salts and 

 the hot solution treated with 20 per cent, magnesium chloride. The precipitate 

 consists mainly of magnesium deoxycholate ; a further quantity is obtained on 

 concentrating the solution and allowing to cool. 



The mother liquor (above) containing magnesium cholate is concentrated 

 to about one-fifth, crystals of magnesium deoxycholeate are filtered off, and 

 the cholic acid precipitated by adding acid. It is at first resinous, but 

 becomes crystalline on standing. 



The crude yellowish crystalline mass of cholic acid is washed, dried in 

 vacuo and recrystallised from hot alcohol. Further crops of crystals, are 

 yielded by concentration of the mother liquor. The remainder is separated 

 by warming the solution with caustic soda, to hydrolyse ethyl cholate, 

 evaporating off the alcohol, dissolving the residue in water and acidifying. 

 The precipitated acid is dried, converted into its sodium salt as in the pre- 

 paration and treated with barium chloride to remove choleate and deoxycholate. 

 The acid is reprecipitated and crystallised from alcohol. The cholalic acid in 

 the last mother liquors is isolated by converting into the sodium salt, evaporat- 

 ing off the. alcohol and acidifying in the presence of ether. 90 per cent, of 

 the crude acid is obtained in a crystalline form melting at 197. It is gener- 

 ally slightly yellow. 



Choleic acid is obtained from the barium salt by grinding with dilute 

 hydrochloric acid. It is almost pure and melts (after drying at 1 10) at 184. 

 Small quantities are recrystallised from acetone, or large quantities from 

 alcohol ; in the latter case, the mother liquors are boiled with caustic soda, 

 the alcohol evaporated, the residue dissolved in water and hydrochloric acid 

 added. The precipitated acid is washed, dried and recrystallised from 

 acetqne. 



Deoxycholic acid is precipitated on grinding the magnesium salt with acid. 

 It is filtered off, washed and recrystallised from acetone. Pure deoxycholic 

 acid is prepared by crystallisation from glacial acetic acid. 225 gm. of 

 cholic acid, 75 gm. of choleic acid and 40 gm. of deoxycholic acid are obtained 

 from i o litres of bile. 



Hair's Method. 



This method is designed to prepare deoxycholic acid. 



240 gm. of sodium hydroxide are dissolved by stirring and heating in 

 4 litres of ox bile. The alkaline solution is boiled gently for 20 hours in an iron 

 digester and its volume reduced by evaporation to 2-3 litres. The hot solution 

 is neutralised to phenolphthalein by adding about 350 c.c. of cone, hydro- 

 chloric acid. A flocculent precipitate of silica, amounting to 1-2 gm. per 

 1000 c.c. of bile is thrown down and filtered off after cooling. The filtrate 

 is acidified to litmus by adding about 50 c.c. of glacial acetic acid. The bile 

 acids separate as a fluid crystalline mass, which is at first white, but rapidly 

 absorbs pigment ; by gentle rotation of the flask, the acids can be made to 

 adhere in a single mass from which the liquid is decanted. The pasty mass 

 retains acetic acid tenaciously and is squeezed to remove the liquid. It is put 

 into a i litre flask and dissolved by heating in about 600 c.c. of glacial acetic 

 acid. The solution is poured into a beaker and allowed to stand for 2-3 days. 

 The crystals which separate and consist of deoxycholic acid, cholalic acid and 

 some fatty acid are filtered off and washed free from pigment with 60 per 

 cent, acetic acid. They are dissolved in about 300 c.c. of hot glacial acetic 

 acid, filtered from silica (?) and the solution allowed to stand. The crystals, 

 mainly deoxycholic acid, are separated, dried between porous tiles and 

 dissolved in about 750 c.c. of 60 per cent, acetic acid. The hot solution is 



