TAUROCHOLIC ACID. 479 



which, when boiled with an alcoholic solution of 

 potassa, is again converted into cholic acid. 



2. Taurocholic acid, C 26 H 45 ]^S0 7 . When fresh ox- 

 bile is mixed with neutral lead acetate, a white, plas- 

 ter-like precipitate is produced, which contains, besides 

 mucus and coloring matter, particularly lead glycocho- 

 late. When the filtered liquid is mixed with basic 

 lead acetate, a similar precipitate is formed, which 

 consists of basic lead glycocholate and lead taurocholate 

 and the lead salts of the fatty acids contained in bile. 

 From this precipitate taurocholic acid can be separated 

 with difficulty. It is more readily obtained from 

 dog-bile, in which no glycocholic acid is contained, or 

 at the most but traces. The alcoholic extract of the 

 dried bile, decolorized with animal charcoal, is eva- 

 porated to dryness, the residue dissolved in a small 

 qauntity of alcohol, and the sodium taurocholate pre- 

 cipitated with ether. To an aqueous solution of this 

 salt lead acetate is added together with some ammo- 

 nia, the precipitate filtered off, dissolved in boiling 

 absolute alcohol, and decomposed by means of sulphu- 

 retted hydrogen. The filtrate from lead sulphide is 

 evaporated down to a small volume at a moderate tem- 

 perature, and then a large excess of ether added to it, 

 which causes the separation of free taurocholic acid 

 as a syrupy mass. This is after a time converted 

 for the greater part into acicular crystals of a silky 

 lustre. It is easily soluble in water and alcohol. When 

 dry it can be heated above 100 without decomposi- 

 tion. When heated with water to 100, it is resolved 

 into cholic acid and taurin (p. 141). It suffers the 

 same decomposition, when its salts, or the bile, are 

 boiled with alkalies or acids, or by the putrefaction 

 of bile. 



Two acids very similar to the two described are 

 hyoglycocholic acid, C 27 H 43 K0 5 , and hyotaurocholic acid, 

 C 27 H 45 NS0 6 , which are contained in the bile of the 

 pig. When boiled with alkalies they are resolved into 

 glycocol, taurin, and an acid very similar to cholic 

 acid, hyocholic acid, C 25 II 40 4 . In goose-bile is also 



