142 



TAUKIN. 



CH 2 (OH). COOH. contains two hydroxyls replaceable by amidogen 

 NH 2 , so that two isomeric amido-derivatives can be formed from 

 it. Of these one is amido-iseth ionic acid CH 2 (OH) . CH 2 . S0 2 

 (NH 2 ), the other amido-ethylsulphonic acid or taurin. 1 



Taurin is stated to occur in traces in the juices of muscles and 

 of the lungs, but it is known chiefly as a constituent of tauro- 

 cholic acid, which is one of the characteristic acids of bile, more 

 especially of the carnivora, and above all, of the dog. 



It crystallises in colourless, regular, four- or more, usually six- 

 sided prisms ; these are readily soluble in water, less so in 

 alcohol. The solutions are neutral. It is a very stable com- 

 pound, resisting temperatures of less than 240 C ; it is not acted 

 on by dilute alkalis and acids, even when boiled with them. It 

 is not precipitated by metallic salts. 



Preparation. Ox-bile is boiled for several hours with dilute 

 hydrochloric acid. The fluid residue is separated from the resin- 

 ous scum, and freed from any remaining traces of bile acids by 

 means of lead acetate, the excess of precipitant being removed by 

 sulphuretted hydrogen. The final filtrate is then concentrated to 

 crystallisation, and the taurin finally purified by recrystallisation 



FIG. 8. TAURIN CRYSTALS. (After Kiihne.) 



from 



water. The use of the lead salt may be omitted in many 

 cases and the taurin purified by several crystallisations from 

 water. 



The behaviour of taurin when introduced into the alimentary canal is 

 remarkable. In the case of man the larger part reappears in the urine 

 in combination with carbamic acid as tauro-carbamic acid. In dogs 

 a large part is excreted unaltered, together with some tauro-carbamic 

 acid. In herbivora (rabbit) on the other hand a portion of it is ex- 



1 Taurin has usually been regarded as identical with amidoisethionic acid. 

 This is not the case. Seyberth, Her. d. d. chem. Gesell. 1874, S. 391. Erlenmeyer, 

 Neu. Rep.f. Pharm. Bd. xxm. (1874), S. 228. 



