1246 



TAURINE. 



Taurine is stated to occur in traces in the juices of muscles 

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

 taurocholic acid, which is one of the characteristic acids of bile, 

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



It crystallizes 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 resi- 

 nous 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 concen- 

 trated to crystallization, and the taurine finally purified by 

 recrystallization from water. The use of the lead salt may 

 be omitted in many cases and the taurine purified by several 

 crystallizations from water- 



FIG. 203. TAURINE CRYSTALS. (After Kiihne.) 



The behaviour of taurine 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 excreted in the urine, but the larger part is oxydized, 

 leading to a large increase of sulphates in the urine together with 

 some hyposulphites. Injected subcutaneously it is largely excreted 

 in an unaltered form. 



Tauro-carbamic acid. NH 2 CO . NH(CH 2 ) . CH 2 . (S0 2 OH). It is 

 most easily obtained as a potassium salt by the action of potassium 

 cyanate on taurine. 



