CHEMISTRY OF THE LEUCOMAINES. 287 



The solution of the salts of the bases, preferably as nitrates 

 or sulphates, must be neutral or faintly acid ; excess of 

 alkali or acid interferes. Such a solution can be obtained 

 by evaporating the filtrate from the guanine in Kossel's 

 method (page 286), and dissolving the residue in nitric 

 acid; this is neutralized with sodium carbonate, using 

 methyl-orange as indicator. On the addition of excess of 

 sodium picrate the adenine is thrown down as a clear yel- 

 low flocculent precipitate. If the precipitation is made at 

 the boiling temperature, on cooling the adenine salt sepa- 

 rates in a crystalline condition and is more easily filtered 

 and washed. After standing fifteen minutes the precipitate 

 is filtered ofi^ by the aid of a suction-pump on a weighed 

 filter, washed with cold water, and dried at 100°. As a 

 correction for the solubility of the adenine picrate, 2.4 mg. 

 per 100 c.c. filtrate can be added to the calculated amount 

 of adenine. 



The hypoxanthine picrate is very soluble, and, therefore, 

 remains in solution. In this it is estimated according to 

 the method described on page 302. 



Adenine, when crystallized from warm or impure solu- 

 tions, is obtained either as an amorphous substance, pearly 

 plates, or in the form of very small microscopic needles ; 

 from dilute cold solutions it separates in long, needle-shaped 

 crystals containing three molecules of water. This water 

 of crystallization is lost on exposure to the air or on heating 

 to 53°, and the crystals become opaque. It is soluble in 

 about 1086 parts of water at the ordinary temperature ; 

 more easily in hot water, from which, on cooling, it recrys- 

 tallizes. The aqueous solution possesses a neutral reaction. 

 The free base is insoluble in ether, chloroform, and alcohol ; 

 soluble in glacial acetic acid, and somewhat in hot alcohol. 

 It dissolves readily in mineral acids, yielding well-crystal- 

 lizable salts. The fixed alkalies dissolve it with ease, but 

 on neutralization of the solution it is reprecipitated. In 

 aqueous ammonium hydrate it is more readily soluble than 

 guanine (which is insoluble, Schindlee), and more diffi- 

 cultly soluble thajn hypoxanthine — a fact which is made use 



