516 



KAHX AND ROSENBLOOM 



As Gmelin points out the figures of Lassaigue are so different from 

 the rest that we must suspect that, through error, he analyzed a different 

 substance. 



From his analytical data, Thaulow suggested C C N 2 H 12 O 4 S 2 as the 

 formula for cystin. Gmelin thought, however, that the formula was 

 C 6 NH 7 S 2 O 4 and states : "According to this formula cystin is similar in 

 composition to urethan and taurin." In 1864 Grote recommended the 

 formula C 3 H 7 NSO 2 but Berzelius and Lehman adopted C 6 H 6 NS 2 4 as 

 the correct empirical formula. 



In 1865 Cramer suggested C 2 H 3 (S H) (N N 2 ) C O 2 H as the 

 formula for cystin. But Dewar and Gamgee in 1870 took issue with this 

 statement. They argued that if Cramer's formula were correct, oxidation 

 of cystin would not yield glycerin but a sulfonic acid. They found that 

 upon reducing cystin with tin and hydrochloric acid, hydrogen 

 sulphid was evolved. From their experiments they suggested CH 2 - 

 (NH 2 )CS COOH as the graphic formula for cystin. This formula 

 would suggest the possibility of cystin yielding methylamin by decom- 

 position with alkalies, but Hoppe-Seyler found that he could not obtain 

 methylamin and that the only nitrogenous body produced is ammonia, 

 and he adopted the Gmelin formula, which he halved, i. e., C 3 NH 6 2 S 

 and, although his hydrogen figures were rather low, he added one hydrogen 

 to satisfy the Gmelin requirements, C 3 NH 7 O 2 S. Kulz in 1884 dis- 

 carded Gmelin's formula, and adopted the one of Thaulow. His hydrogen 

 analyses were too high for the Gmelin formula, but agreed exactly with 

 the formula of Thaulow. 



Baumann(a) corroborated the work of Kulz in an entirely different 

 series of experiments. Upon reduction of cystin with tin and hydro- 

 chloric acid, he obtained a new substance which was a reduction product 

 of cystin, and which upon analysis gave figures which approximated the 

 Gmelin formula, C 3 H 7 NSO 2 . He called this substance cystein, and 

 he called attention to the similarity of cystein to a mercaptan which 

 upon oxidation yields a disulphid : 



2 (C 3 H 6 N0 2 SH) + O = C 3 H 6 N0 2 S 



(Cystein) / -f H 2 O 



C 3 H 6 NO 2 S 

 Cystin 



