THYMINE. 195 



varies with the dilution. This reaction which, as remarked above, is also 

 given by cytosine, depends upon the fact that dibromoxyhydrouracil 

 is first formed, and from this, by the action of the barium hydroxide, 

 first isodialuric and then dialuric acid is produced, both of which give 

 the coloration. In regard to the preparation of uracil see KOSSEL and 



STEUDEL. 1 



HN CO 



I I 

 Thymine, C5H 6 N 2 O2, = OC C.CH 3 (5-methyluracil). This body, 



HN CH 



which is identical with nucleosin obtained by SCHMIEDEBERG from sal- 

 mo-nucleic acid, was first prepared by KOSSEL and NEUMANN from 

 thymus-nucleic acid, and then by other investigators, especially LEVENE 

 and MANDEL, from other animal nucleic acids. FISCHER and ROEDER and 

 later GERNGROSS 2 have prepared it synthetically. 



Thymine crystallizes in small leaves grouped in stellar or dendriform 

 clusters or, rarely, in short needles (GULEWITSCH 3 ) . It deflagrates at 

 318 C. and melts at about 321 and sublimes. It is soluble with diffi- 

 culty in cold water, more soluble in hot water, and insoluble in alcohol. 

 It behaves like uracil toward ammonia or baryta-water and silver nitrate. 

 Thymine is precipitated by phosphotungstic acid, especially when impure. 

 Bromine-water is decolorized by thymine, producing bromthymine. 

 For its detection we make use of the sublimation, the behavior toward 

 silver nitrate, and its elementary analysis. 



MEYERS 4 has prepared compounds of pyrimidine bases with several metals 

 such as K, Na, Pb, Hg and he considers it incorrect to call the pyrimidine bodies 



In regard to the methods of preparation see KOSSEL and NEUMANN 

 and W. JoNES, 5 



The purine and pyrimidine bodies stand in close chemical and phys- 

 iological relation to each other and for this reason the question has 

 been repeatedly raised whether the pyrimidine bases might not be formed, 

 at least in part, from the purine bases by the action of acids. Thus 

 far no conclusive investigations have been made supporting this view, 

 while on the contrary the investigations of STEUDEL 6 seem to contradict 

 such a view. 



1 Zeitschr. f. physiol. Chem., 37. 



2 Schmiedeberg, Arch. f. exp. Path. u. Pharm., 37; Kossel and Neumann, Ber. 

 d. d. chem. Gesellsch., 26 and 27; Mandel and Levene, Zeitschr. f. physiol. Chem., 46 

 47, 49, 50; E. Fischer and Roeder, ibid., 34; Gerngross, ibid., 38. 



3 Zeitschr. f. physiol. Chem., 27. 



4 Journ. of biol. Chem., 7. 



5 Kossel and Neumann, 1. c., and W. Jones, Zeitschr. f. physiol. Chem., 29, 461. 



6 Zeitschr. f. physiol. Chem., 51 and 53 (against Burian). 



