TAUROCHOLIC ACID. 171 



Taurine, C 2 H 7 NS0 3 . 1. Mix ox bile with hydro- 

 chloric acid, filter the liquid from the precipitate which 

 will fall, evaporate the filtrate till it separates into a 

 viscous resin and a watery liquid ; pour off the liquid 

 and rinse the resin with water. Unite the two liquids, 

 and evaporate to a small bulk ; allow to crystallise ; 

 taurine and sodium chloride crystallise out ; the 

 taurine is separated by picking out the crystals, which 

 can be purified by recrystallisation. 



2. Taurine crystallises in large transparent glassy 

 crystals, which when heated first melt and then 

 blacken. It is moderately soluble in water, nearly 

 insoluble in alcohol. 



3. Melt some taurine with caustic potash ; treat 

 the residue with dilute sulphuric, holding a slip of 

 paper moistened with lead acetate solution over the 

 mass ; sulphuretted hydrogen is evolved, turning the 

 lead paper black ; sulphurous acid is also evolved, and 

 sulphur is left as a residue. This proves the existence 

 of sulphur in taurine. 



Taurocholic acid, C 26 H 45 NS0 7 . 1. Extract some 

 dog's bile with alcohol, decolorise by animal charcoal, 

 and evaporate the extract to dryness. Dissolve the 

 residue in a small quantity of absolute alcohol and 

 ether ; on standing in the cold sodium taurocholate is 

 precipitated in crystals. 



2. Precipitate ox bile with neutral lead acetate, and 

 filter. Precipitate with basic lead acetate, and wash 

 the collected precipitate ; dissolve it in boiling alcohol, 



