iv THE SULPHUR-RADICALS 169 



derived was precipitated by phosphotungstic acid, that it therefore was 

 a base, and Miiller and Seemann l and Blum and Yaubel 2 also described 

 a sulphur-containing base of unknown constitution amongst the dis- 

 sociation-products of egg-white. Amongst these substances, cystin 

 (for full account see p. 56) must be considered to be the primary 

 dissociation -product, as it has been found in large quantities by 

 Morner, 3 Embden, 4 and Patten 5 after dissociation with acids and after 

 digestion with trypsin. Cystein is formed secondarily, according to 

 Patten. Besides a-thiolactic acid, Friedmann 6 believes to have found 

 its disulphide. Sulphuretted hydrogen and the mercaptanes may be 

 derived directly from it, while there is some difficulty in deriving 

 ethyl-sulphide. The interrelation between a-thiolactic acid and cystin 

 is explained on p. 83. The explanations of Baumann 7 are based 

 on the older formula, according to which cystein is a-amino-a-thiolactic 

 acid, and are therefore antiquated. Morner has found cystins so 

 constantly and in such preponderating amounts, that by comparison 

 thiolactic acid and Drechsel's base are of very subordinate importance. 



Cystin splits off a part of its sulphur as sulphuretted hydrogen on 

 being boiled with sodium hydrate, and therefore behaves exactly as do 

 albumins (Baumann, 8 Schulz, 9 and Suter 10 ). In testing for sulphur, 

 albumins are boiled, as a rule, with sodium hydrate and lead acetate, 

 when, owing to the formation of lead sulphide, a black precipitate, or 

 at least a dark coloration, is produced. Schulz and Suter have shown 

 that sulphur is split off very gradually, eight to nine hours being 

 required to obtain the maximal splitting-off. During this process the 

 sulphuretted hydrogen may become oxidised, for which reason Schulz 

 made his determinations in an atmosphere of coal gas, substituting at 

 the same time zinc for lead. The conditions are much more difficult 

 when we are dealing with the albumins themselves instead of working 

 with cystin, for the latter must be liberated from the rest of the 

 albumin-molecule before it can be acted upon any further. 



A great deal of importance used to be attached to the idea that 

 albumins contained their two sulphur atoms bound up in different ways 

 the one in the form of sulphuretted hydrogen, the other in a non-dis- 



J. Seemann, Dissertation, Marburg, 1898. 



F. Blum and W. Vaubel, J&wrn. f. prakt. Chem. [2], 57. 365 (1898). 



K. A. H. Morner, Zeitschr.f. physiol. Chem. 28. 595 (1899), 34. 207 (1901). 



G. Embden, ibid. 32. 94 (1900). 

 F. A. Patten, ibid. 39. 350 (1903). 



E. Friedmann. Hofmeisters Beitrdge, 3. 184 (1902), 4. 486 (1903). 

 E. Baumann, Zeitschr.f . physiol. Chem. 20. 583 (1895). 



E. Baumann, ibid. 8. 299 (1884). 



F. N. Schulz, ibid. 25. 16 (1898). 

 10 F. Suter, ibid. 20. 564 (1895). 



