AJDENIN. 357 



adapted for the qualitative recognition of adenin, especially in the 

 presence of guanin, which gives no such compound. 



Adenin lead was prepared by Kriiger by adding a solution of 

 adenin and sodium hydrate to an aqueous solution of lead acetate. 

 It forms lusterless needle-shaped crystals. The composition appears 

 to be CjHjPbNj . On friction it becomes strongly electric. Heated 

 with methyl iodid it gives rise to addition products (see page 363). 



The silver salt of adenin, CjH^AgNj, is formed when silver 

 nitrate is added in molecular proportion to a boiling ammoniacal 

 solution of adenin. On heating this compound for thirteen hours 

 at 130° with methyl iodid no appreciable change results (Kriiger), 

 although Thoiss obtained a compound, presumably a methyl addition 

 product. An excess of silver nitrate produces, in the cold, the com- 

 pound CjHjAgjNj + HjO, which is converted slowly in the cold, 

 immediately on warming, into the other salt, according to the 

 equation : 



2(C,H3Ag,N, + HP) = 2C,H,AgN, + Ag,0 + H,0. 



Owing to this instability the two compounds are always found to- 

 gether in varying proportion. Both are difficultly soluble in water, 

 and in ammonia even at the boiling-point. The precipitation of 

 adenin by an ammoniacal silver solution is complete, and is there- 

 fore available for quantitative estimation. The precipitate of adenin, 

 as well as of other xanthin bases, is soluble in excess of sodium 

 hyposulphite (Kossel). 



Adenin silver nitrate, CjHjNj.AgNOj (Ag= 35.4 per cent.), cor- 

 responds to the similar hypoxanthin and guanin salts. It is obtained 

 by dissolving the above silver compound in hot nitric acid; and 

 from this solution, on cooling, it separates in needle-shaped crystals, 

 which are not permanent. This lack of stability, as compared with 

 the permanent hypoxanthin silver nitrate, was first pointed out by 

 Kossel and was thought to be due to the loss of nitric acid in wash- 

 ing, and also by heating at 100°. Bruhns, however, has shown that 

 the acidity of the wash-water is indicated by litmus, but not by 

 methyl orange, which is not colored red by silver nitrate. It would 

 seem that adenin, as well as hypoxanthin, and possibly xanthin, 

 form silver compounds containing one and two molecules of silver 

 nitrate ; the greater the quantity of silver nitrate used the higher is 

 the per cent, of silver, i. e., the more of the latter compound is 

 formed. These are very unstable, and are decomposed by dilute 

 nitric acid, more so by water, into silver nitrate, and the com- 

 pound containing one molecule of silver nitrate. We have in this 

 behavior an interesting case of mass action and chemical equili- 

 brium between adenin, silver nitrate, nitric acid and water. Ammo- 

 nium hydrate removes the nitric acid from this as easily as from the 

 hypoxanthin compound, and there is formed, according to the com- 



