232 CONJUGATED ACIDS. 



becomes converted into taurine, whose properties we have already 

 described at p. 179. By elementary analyses of a mixture of pure 

 alkaline glycocholates and taurocholates, obtained directly from 

 fresh bile, Strecker has further confirmed his view regarding the 

 composition of this acid. Pure taurocholic acid must, therefore, 

 contain 6*213$ of sulphur, while its atomic weight must= 6437*5 

 and its saturating capacity be 1'553. 



Combinations. The alkaline taurocholates dissolve readily in 

 water and in alcohol, but are perfectly insoluble in ether; they 

 have no reaction on vegetable colours, and attract water from the 

 atmosphere, but do not deliquesce ; when kept for a long time in 

 contact with ether they crystallise ; their aqueous solutions have a 

 sweet taste with a bitter after-taste, and do not decompose when 

 evaporated, or when exposed to the air, provided they be pure. 

 These salts when heated melt and burn with a bright smoky 

 flame. Carbonic acid does not decompose their alcoholic solution ; 

 their aqueous solution is not precipitated by acids, nor by the 

 alkaline sulphates or chlorides (like the alkaline hyocholates), but 

 by concentrated alkaline solutions; it is not precipitated by 

 the salts of baryta, lime, or magnesia, even on the addition of 

 ammonia, or by neutral acetate of lead ; but on the addition of 

 basic acetate of lead, there is a plastery precipitate which dissolves 

 in boiling water, and even more freely in boiling alcohol, and is 

 also soluble in an excess of acetate of lead. Nitrate of silver, even 

 after the addition of ammonia, does not precipitate the tauro- 

 cholates, neither does corrosive sublimate, but precipitates are 

 induced by nitrate of suboxide of silver, and protochloride of tin. 

 Nitrogenous substances, mucus for instance, set up a process of 

 decomposition in solutions of the alkaline taurocholates, which 

 may be readily ascertained by the circumstance that the solutions 

 then become precipitable by dilute acids. The products which are 

 formed are taurine, alkaline cholates or choloidates, and probably 

 certain combinations of these substances with taurocholic acid that 

 has escaped decomposition. In aqueous solutions of pure alkaline 

 taurocholates, these decompositions are not observed to occur. 



Preparation. We have already remarked, that this acid has 

 never yet been prepared in a state of complete purity. In order 

 to separate it as thoroughly as possible from the glycocholic acid 

 which always accompanies it, we in the first place remove from 

 the purified ox-bile the greater part of the glycocholic acid and of 

 the fatty acids by means of neutral acetate of lead, and then pre- 

 cipitate by basic acetate of lead, to which we may add a little 



