CHEMISTRY OF THE LEUCOM AINES. 291 



solving adenine in hot, dilute, aqueous oxalic acid, from 

 which solution, on cooling, it separates as a voluminous, 

 difficultly soluble precipitate of roundish masses which are 

 composed of long, delicate needles. The oxalates of guanine, 

 hypoxanthine, and xanthine are more easily soluble than 

 that of adenine, and exhibit, moreover, a different appear- 

 ance. 



The picrate, C5HA-C6H,(NO,)30H + H^O, is thrown 

 down as a bright yellow flocculent precipitate, when aqueous 

 solutions of adenine salts are treated with sodium picrate. 

 Eecrystallized from hot water it forms bright-yellow, very 

 voluminous bunches of long fine needles, which, on drying, 

 acquire a silky lustre and form a felted mass. It is diffi- 

 cultly soluble in cold water (1 : 3500) ; more readily in hot 

 water and in alcohol (96 per cent.) ; is insoluble In dilute 

 acids. The water of crystallization is not lost on exposure 

 to air but is driven off at 100° ; the salt then remains un- 

 changed even at 220°. A cold concentrated aqueous solu- 

 tion of the salt treated with one-tenth its volume of cold con- 

 centrated solution of sodium picrate produces a precipitate 

 of short fine needles consisting of most of the adenine picrate 

 (five-sevenths). The solubility of the picrate can thus be 

 reduced to as low as 1 : 13750, and on this fact is based the 

 quantitative method of Bkuhns. The salt can also be 

 obtained in its characteristic groups by combining cold 

 saturated aqueous adenine solution (1 : 1086) with picric 

 acid ; with sodium picrate, however, adenine gives no pre- 

 cipitate, since the picrate is soluble in an equivalent quan- 

 tity of sodium hydrate. Thus Is explained Kossel's 

 statement that adenine forms an easily soluble compound 

 with picric acid. Heated on a platinum foil it burns slowly 

 and leaves considerable carbon residue. The very bright 

 yellow color of the salt serves to distinguish it from most 

 of the other picrates, especially guanine picrate. 



The platinochloride, (C5H5F5.HCl)jPtCl^, crystallizes 

 from dilute aqueous solution in small yellow needles. The 

 concentrated aqueous solution of this salt, when boiled for 

 some time, decomposes, with the separation of a clear. 



