CHEMISTET OF THE LEUCOMAINES. 305 



chloride forms a yellow, crystalline double salt, having the 

 composition CsH.Np.HCl.PtCl,. 



The picrate forms yellow prisms easily soluble in water, 

 which solution is not affected as that of adenine by sodium 

 picrate. 



Hypoxanthine silver, CjHjAgjN^O.HjO. All attempts 

 to obtain a compound containing but one atom of silver 

 in the molecule, corresponding to the adenine compound 

 CjH^AglT,, have failed. The above compound was first 

 prepared by Steecker, and given the formula C^H^N^O. 

 AgaO ; but the former is preferable, since on heating at 120° 

 two and a half molecules of water are lost and 



2C5H2Ag2Np + H2O (Ag = 60.2 per cent.) results. 



At 140°-150° it loses again in weight and becomes gradu- 

 ally gray ; on exposure to air it absorbs moisture. In this 

 form hypoxanthine can be estimated quantitatively (see 

 page 302) ; the presence of sodium picrate does not interfere, 

 but chlorides, etc., do. It is insoluble in hot water. The 

 compound, C5H2Ag2N^0.3H20, is obtained in the form of 

 microscopic needles, by treating pure hypoxanthine silver 

 nitrate with excess of aqueous ammonia. On boiling with 

 ammonia-water it is but slightly dissolved, and appears to 

 slowly lose a part of its water of crystallization. As a 

 result of the decomposition one-half of the hypoxanthine 

 passes into solution and can be recovered on boiling with 

 addition of silver nitrate in the crystalline form ; or in the 

 cold, as the usual amorphous precipitate, C,H2Ag2N^O.H20. 

 Hypoxanthine silver nitrate, CjH^N^O.AgNOj, (Ag = 

 35.29 per cent.), is the best-known compound ; its formula 

 was established by Steeckek. It is obtained by dissolving 

 the above precipitate, produced by addition of silver 

 nitrate to an ammoniacal solution of the base, in hot nitric 

 acid, specific gravity 1.1 ; on cooling the hypoxanthine 

 silver nitrate crystallizes in the form of tufts of microscopic 

 needles or plates. Heated at 100°-120° it remains con- 

 stant in weight; the quantity of silver present, when deter- 

 mined, is always somewhat higher than the theoretical, 



