394 METHODS FOR THE ANALYSIS OF BILE. [BOOK II. 



sulphur, whence the amount of taurocholic acid is determined. It is 

 evaporated to dryness in a silver basin arid then ignited with 

 caustic soda and potassium nitrate, or it is treated by Carius' method 

 (heating in a sealed tube with strong pure nitric acid). Whichever 

 method is employed for oxidising the sulphur, the amount of sulphuric 

 acid is determined in the usual manner by precipitating with barium 

 chloride, &c. 



The fraction y serves for the estimation of the glykocholic acid, 

 taurocholic acid and the fatty acids. If necessary, it should be 

 decolourized by means of recently ignited pure animal charcoal, the 

 latter being afterwards thoroughly washed with alcohol and the 

 combined alcoholic fluids concentrated on the water bath and brought 

 up to a known volume. The specific rotation of the alcoholic solution 

 is now determined (see Vol. i. 1st edition, p. 7 et seq.), 



Either the whole of the alcoholic solution, or a known fraction of 

 it, is now evaporated so as to expel the alcohol ; the watery solution 

 of the residue is then placed, lege artis, in a thick and hard tube in 

 which have been previously placed at least 5 grms. of dry caustic 

 baryta. The tube is then sealed about a decimeter above the level 

 of the fluid, and, after being allowed to cool, the tube is thoroughly 

 shaken and then heated in the oil bath at 110 120 C. for ten or 

 twelve hours. The tube is, thereafter, cautiously opened, the liquid 

 is poured into a beaker, the tube thoroughly washed, and C0 2 is 

 then passed through the solution until no further precipitation of 

 barium carbonate occurs. It is then heated to boiling and filtered, 

 at this temperature, through a hot-water funnel. 



Fm. 23. A HOT-WATER FUNNEL. 



The projecting tube B permits of the water being heated to boiling during the pro- 

 gress of nitration, the steam being allowed to escape through E. 



The filtrate contains barium cholalate, besides glycocine and 

 taurine, whilst the precipitate consists of barium salts of the fatty 

 acids and of oleic acid, mixed with much barium carbonate. From 

 this precipitate, the fatty acids and oleic acid are obtained by decom- 

 posing with dilute hydrochloric acid, repeatedly extracting with ether 



