194 THE PROTEIN SUBSTANCES. 



and JOHNSON l have also prepared it synthetically. It is transformed 

 into uracil by the action of nitrous acid. 



The free base is soluble with difficulty in water (129 parts) and crystal- 

 lizes in thin leaves with a mother-of-pearl luster. It is insoluble in ether 

 and soluble with difficulty in alcohol. The double compound with platinum 

 chloride, the crystalline picrate, the nitrate, and the picrolonate are 

 of importance in the detection of cytosine. This base is precipitated 

 by phosphotungstic acid and by silver nitrate in the presence of an 

 excess of barium hydroxide, which fact is of importance in the detection 

 of cytosine (KUTSCHER). The double bismuth-potassium iodide gives 

 a brick-red precipitate. Cytosine gives the murexid reaction with 

 chlorine-water and ammonia (see Chapter XIV), and also the reaction 

 described by WHEELER and JOHNSON under uracil. In regard to 

 preuaration see KOSSEL and STEUDEL 2 and also KUTSCHER. S 

 HN CO 



I I 

 UracU, C4H 4 N 2 O2, = OC CH (2, 6-dioxypyrimidine), was first 



I II 

 HN CH 



obtained by ASCOLI and KOSSEL from yeast nucleic acid and later from 

 various complex nucleic acids, perhaps secondarily from the cytosine as a 

 cleavage product. The synthetical preparation was first accomplished by 

 E. FISCHER and RoEDER. 4 



Uracil crystallizes in needles which cluster in rosettes. On careful 

 heating it sublimes in part undecomposed, but develops red vapors and 

 decomposes in part. It is readily soluble in hot water, but less so in cold 

 water, and nearly insoluble in alcohol and in ether. Uracil is readily 

 soluble in ammonia. It is precipitated by mercuric nitrate, but not by 

 phosphotungstic acid. It is precipitated by silver nitrate only on the 

 careful addition of ammonia or baryta-water. Uracil gives the WEIDEL 

 reaction and the following reaction described by WHEELER and JOHN- 

 SON . 5 The uracil solution is treated with bromine-water until it is per- 

 manently cloudy and then treated with baryta-water, when a purple or 

 violet-colored precipitate appears almost immediately. The coloration 



1 Amer. chem. Journ., 29. 



2 Zeitschr. f . physiol. Chem., 37 and 38. 



3 Ibid., 38. As it is not excluded, but rather probable according to Wheeler, that 

 besides thymine also other related pyrimidine bases such as isocytosine, 6-amino 

 pyrimidine and 6-oxpyrimidine can be formed in the hydrolytic cleavage of the nucleic 

 acids, Wheeler has prepared salts and compounds of these bodies and described them 

 as a matter of comparison, Journ. of biol. Chem., 3. 



4 Ascoli, Zeitschr. f. physiol. Chem., 31; Kossel and Steudel, ibid., 37; Levene, 

 ibid., 38, 39; Levene and Mandel, ibid., 49; E. Fischer and Roeder, Ber. d. d. chem. 

 Gesellsch., 34. 



6 Journ. of biol. Chem., 3. 



