142 TAURIN 



conclusive, for in most cases the sarkosin is largely excreted in an 

 unaltered condition, methyl-hydantoic acid being formed in very minute 

 quantities if at all 1 . It is further interesting to note that the purely 

 chemical reactions which most readily yield methyl-hydantoic acid out 

 of the body, involve the interaction of sarkosin with cyanic compounds 

 such as ammonium or potassium cyanate 2 . Moreover it has been shown 

 that at the temperature of the body sarkosin and urea in solution do 

 not yield methyl-hydantoic acid, although they do in presence of baryta, 

 especially when boiled 3 . These facts show that Schultzen's experiments 

 do not strongly favour the carbamic-acid origin of urea ; they further 

 show that the methyl-hydantoic acid is probably not formed by a direct 

 union of sarkosin and urea and are, from a purely chemical point of 

 view, rather in favour of a cyanic origin of urea. 



3. Taurin. C 2 H 7 NSO 3 . [CH 2 (NH 2 ) . CH 2 (SO 2 . OH)]. Amido- 

 ethylsulphonic acid.) 



Isethionic acid, CH 2 (OH) . CH 2 . S0 2 (OH), like glycolic acid, 

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

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

 Of these one is amido-isethionic acid CH 2 (OH) . CH 2 . SO 2 (NH 2 ), the 

 other amido-ethylsulphonic acid or taurin 4 . 



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 taurocholic 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 compound, resisting tem- 

 peratures 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 hydro- 

 chloric acid. The fluid residue is separated from the resinous scum, and 

 freed from any remaining traces of bile acids by means of lead acetate, 

 the excess of precipitant being removed by sulphuretted hydrogen. 



1 Baumann u. von Mering, Ibid. 1875, S. 584. E. Salkowski, Ibid. S. 638. 

 Also Zt. f. physiol. Chem. Bd. iv. (1880), Sn. 55, 101. But see also Schiffer, Ibid. 

 Bd. v. (1881), S. 257; Bd. vn. (1883), S. 479. 



2 Baumann u. Hoppe-Seyler, Ber. d. d. diem. Gcsell 1874, S. 34. Salkowski, 

 Ibid. S. 116. 



3 Baumann u. Hoppe-Seyler, loc. cit. Baumann, Ibid. S. 237. 



4 Taurin has usually been regarded as identical with amido-isethionic acid. 

 This is not the case. Seyberth, Ber. d. d. chem. Gesell. 1874, S. 391. Erlemneyer, 

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



