128 THE BILE. 



sodium taurocholate by saturating the liquid with sodium chlorid. 

 Filter and add hydrochloric acid until the solution contains 2 

 per cent. If a precipitate of salts appears remove it by nitration 

 and from the filtrate precipitate the taurocholic acid with ether. 

 It should be filtered immediately and can be recrystallized in the 

 same manner, being then obtained in needles or prisms. Its 

 preparation is more difficult than that of the glycocholic acid. 



274. Add the solution of the taurocholic acid acidified with 

 sulphuric acid to solutions of albumin or peptones and observe 

 that they form insoluble compounds. 



275. PBEPAEATION OF TATJKIN. Mix dog-bile with an 

 excess of concentrated hydrochloric acid, and evaporate the liquid 

 to a small volume by boiling. Pour off the solution from the 

 resinous mass of acids which have separated, and evaporate this 

 liquid until the sodium chlorid has, for the most part, crystallized 

 out. Filter, and evaporate the filtrate to dryness. From the 

 residue dissolve the glycocoll with alcohol, then the insoluble 

 taurin in the smallest possible quantity of hot water. 'On cool- 

 ing the taurin crystallizes out in four-sided prisms. 



276. PREPARATION or CHOLESTERIN. Biliary cal- 

 culi or gall-stones are the best source of cholesterin. Pow- 

 der the calculus, remove the bile by boiling water, then 

 dissolve the cholesterin in boiling alcohol, and filter while 

 hot. It separates from the filtrate on cooling. The in- 

 soluble residue, which consists largely of compounds of the 

 biliary coloring matters, can be used for the preparation of 

 these. The cholesterin may be further purified by dis- 

 solving it in an alcoholic solution of potassium hydrate 

 with the aid of heat. After it separates on cooling, wash 

 well with water on the filter, then recrystallize from a 

 mixture of alcohol and ether. 



277. Examine the crystals under the microscope. 

 They are in the form of large rhombic tables or plates. 



278. To a crystal of cholesterin in a test-tube or 

 under the microscope add a drop of concentrated sulphuric 



