CHEMISTRY OF THE liEUCOM AINES . 293 



an interesting case of mass-action and chemical equilibrium 

 between adenine, silver nitrate, nitric acid and water. 

 Ammonium hydrate removes the nitric acid from this as 

 easily as from the hypoxanthine compound, and there is 

 formed, according to the composition of the original salt, a 

 varying mixture of CjH^AgNj and CjHjAgjN, + Hz^- 

 The solubility in nitric acid is about the same as that of 

 hypoxanthine silver nitrate. 



Adenine silver picrate, C5H^AgN5.C5H2(NO2)30H + 

 HjO, is obtained as an amorphous voluminous yellow pre- 

 cipitate when silver nitrate is added to a cold aqueous solu- 

 tion of adenine picrate. If the latter solution is previously 

 raised to the boiling-point the precipitate then soon becomes 

 crystalline and rapidly subsides. The adenine can thus be 

 almost wholly removed from solution. The crystalline 

 form loses its water of crystallization at 120°, while the 

 amorphous form does not appreciably decrease in weight and 

 its composition does not appear to be as constant as that of 

 the corresponding hypoxanthine compound. On treatment 

 with ammonium hydrate the picric acid is removed, and 

 adenine silver, CjH^AgNj, is left, stained yellow by traces 

 of picric acid. 



Adenine-mercury picrate, (C^B.^N^).^lig.2C^U2{1^02\OH, 

 can be prepared by treating a hot concentrated aqueous 

 solution of adenine picrate with an excess of sodium picrate- 

 and then with mercuric chloride. It forms a yellow gran- 

 ular crystalline precipitate (microscopic needles) which rap- 

 idly subsides and increases in quantity as the solution cools. 

 Its composition apparently varies, containing one to two 

 molecules of water, according to the temperature of the 

 solution. One molecule is given off at 100°, and the second 

 at 105°-120°. The latter preparation, then, on exposure to 

 the air, rapidly absorbs one molecule of water. The ob- 

 ject of the sodium picrate in the precipitation is to combine 

 ■with the hydrochloric acid, which is set free. The precipi- 

 tate produced by mercuric chloride in cold adenine picrate 

 solution shows yellow and white granules, and is not homo- 

 geneous. Beuhns considers it to be a mixture of the aden- 

 ine-mercury picrate and the compound CjH^NjHgjjClj ; if 



