THE PROTEIDS 



427 



CO NH=CNH NH CO 



2 CH 5 CH CO CH CO CH 



II II II I II 



3 N 4 CH NH CH NH CH 



Pyrimidin. Uracil. Cytosin. 



CO CCH 3 CO 



NH CO 



CO 



NH CH 



Thymin. 



NH CO 



Alloxan. 



Uracil was first prepared by Ascoli l from yeast ; its constitution 

 determined by Steudel, 2 and confirmed by the synthesis of E. Fischer. 3 

 It crystallises in needles arranged in a rosette-like manner ; does not 

 sublime without undergoing decomposition ; is readily soluble in hot 

 water, slightly soluble in cold, and hardly soluble in alcohol and ether ; 

 it is readily soluble in ether. It is precipitated by phosphotungstic 

 acid and mercuric sulphate. 



Cytosin was discovered by Kossel and Neumann ; 4 its constitution 

 found out by Kossel and Steudel, 5 and confirmed by the synthesis of 

 Wheeler and Johnson. 6 It resembles thymin as regards solubility; to 

 isolate it, recourse is had to precipitation with silver nitrate and 

 barium hydrate ; 7 for analysis the double salt with platinum-chloride 

 is used. 



Thymin was discovered by Kossel, 8 and described by his pupils 

 Jones 9 and Gulewitsch. 10 Its constitution was cleared up by Steudel, 11 

 and confirmed by the synthesis of E. Fischer. 12 It crystallises in small 

 needles or dendritic platelets belonging to the rhombic system. 

 Thymin is not precipitated by silver nitrate, hydrochloric acid, and 

 nitric acid, but by silver nitrate and barium-hydrate ; ammonia pre- 

 cipitates, but redissolves, if used in excess. Thymin being slightly 

 soluble in cold water, and readily soluble in hot water, may therefore be 

 recrystallised from water. When carefully heated it sublimes ; when 

 heated more strongly it melts at 290. Thymin is identical with what 

 Miescher and Schmiedeberg have described as nucleosin. 



1 A. Ascoli, Zeitschr. f. physiol. Chem. 31. 161 (1900). 



2 H. Steudel, ibid. 30. 539 (1900) ; 32. 241 (1901). 



3 E. Fischer and G. Boeder, Ber. d. deutsch. chem. Ges. 34. III. 3751 (1901). 



4 A. Kossel and A. Neumann, ibid. 27. 2215 (1894). 



5 A. Kossel and H. Steudel, Zeitschr. /. physiol. Chem. 37. 177 (1902) ; 37. 377 

 (1903) ; 38. 49 (1903). (Here is given a full description.) 



6 H. L. Wheeler and T. B. Johnson, Amer. Chem. Journ. 29. 492 (1903), and ibid. 

 32. 342 (1904). 7 F. Kutscher, Zeitschr. f. physiol. Chem. 38. 170 (1903). 



8 A. Kossel and A. Neumann, Ber. d. deutsch. chem. Ges. 26. 2753 (1893) ; Zeitschr. 

 f. physiol. Chem. 22. 388 (1896) ; A. Kossel and H. Steudel, ibid. 29. 303 (1900). 



9 W. Jones, ibid. 29. 20 (1899) ; 29. 461 (1900). 



10 W. Gulewitsch, ibid. 27. 292 (1899). 



11 H. Steudel, Zeitschr. f. physiol. Chem. 30. 539 (1900) ; 32. 241 (1901). 



12 E. Fischer and G. Roeder, Ber. d. deutsch. chem. Ges. 34. III. 3751 (1901). 



Of THE 



UNIVERSITY 



