CHAP. IV.] GLYKOCHOLIC ACID. 295 



Modes of 1. From Plattners 'crystallised bile' (see p. 291). 



preparation. rp ne cr y s t a lline precipitate obtained by adding ether 

 to a solution of dried decolourised bile in absolute alcohol is 

 dissolved in water and dilute sulphuric acid is added to the 

 solution, until a permanent and dense turbidity is produced. The 

 liquid is set aside when, after some hours, glykocholic acid separates 

 in the form of fine silky needles. It is collected on a filter, washed 

 with distilled water, pressed between filter paper and then dissolved 

 in alcohol, only as much of this liquid being employed as suffices 

 to dissolve the acid. To the alcoholic solution, many times its 

 volume of ether is added, when pure glykocholic acid separates out, 

 in the form of long silky needles. 



2. By precipitation with lead acetate. Decolourised extract of 

 ox bile is dissolved in water and the solution is treated with a 

 solution of lead acetate which produces a precipitate composed 

 almost entirely of glykocholate of lead. This precipitate is collected, 

 washed, drained, and is mixed with alcohol. A solution containing 

 an excess of sodium carbonate is then added and the mixture 

 evaporated to dry ness. In this process a double decomposition 

 occurs, which results in the formation of lead carbonate and sodium 

 glykocholate. From the dry residue which, in addition to these 

 salts, contains an excess of sodium carbonate, the sodium glyko- 

 cholate is dissolved out by means of absolute alcohol. The alcoholic 

 solution is then evaporated to dryness, the residue dissolved in water, 

 decolourised by heating with pure animal charcoal, filtered and 

 treated with dilute sulphuric acid, which causes the separation of 

 glykocholic acid. This process is very instructive for the student, 

 but does not so readily, or so uniformly, yield a pure product as the 

 one first described. 



3. By Hufners method 1 . Perfectly fresh ox bile is treated 

 with a few drops of strong hydrochloric acid which causes the 

 separation of the mucoid nucleo-albumin. The liquid is then 

 filtered and to each 100 c.c. of the filtrate 5 c.c. of concentrated 

 hydrochloric acid are added. The liquid being placed in a stoppered 

 cylinder, 30 c.c. of ether are added for every 100 c.c. of bile, the 

 whole shaken and placed in the cold. In the most favourable 

 cases, the separation of crystals of glykocholic acid commences at 

 once ; usually, however, some hours elapse before the separation 

 occurs, when the mixture is found to have been converted into an 

 almost solid magma of crystals. The ether having been diluted, the 

 crystals are washed in ice-cold water until the washings are colour- 

 less; they are then dissolved in the smallest possible quantity of 

 boiling water which, on cooling, deposits them in a colourless and 

 pure condition. 



1 G. Hiifner, ' Schnelle Darstellung von Glykocholsaure. Journ. f. prakt. Chemie, 

 Vol. x. (1874), p. 267. 



