292 BACTERIAL POISONS. 



yellow powder, which is but slightly soluble in cold water, 

 and has the composition C 5 H 5 N 6 .HCl.PtCl 4 . 



The aurochloride, on evaporation, yields very charac- 

 teristic forms. 



The silver salt of adenine, C 5 H 4 AgN 8 , is formed when 

 silver nitrate is added in molecular proportion to a boiling 

 ammoniacal solution of adenine. An excess of silver 

 nitrate produces, in the cold, the compound C 5 H 3 Ag 2 N 6 + 

 H 2 O, which is converted slowly in the cold, immediately on 

 warming, into the other salt, according to the equation : 



2(C 9 H 3 Ag 2 N 5 + H 2 0) = 2C 8 H 4 AgN 5 + Ag 2 O + H 2 O. 



Owing to this instability the two compounds are always 

 found together in varying proportion. Both are difficultly 

 soluble in water, and ammonia even at the boiling-point. 

 The precipitation of adenine by an ammonical silver solu- 

 tion is complete, and is therefore available for quantitative 

 estimation. 



Adenine silver nitrate, C 5 H 5 N 5 . AgNO 3 , (Ag = 35.4 per 

 cent.), corresponds to the similar hypoxanthine and guanine 

 salts. It is obtained by dissolving the above silver com- 

 pounds in hot nitric acid ; and from this solution, on cool- 

 ing, it separates in needle-shaped crystals, which are not 

 permanent. This lack of stability, as compared with the 

 permanent hypoxanthine silver nitrate, was first pointed 

 out by KOSSEL, and was thought to be due to loss of nitric 

 acid in washing, 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. The reaction is, there- 

 fore, due not to free nitric acid, but to silver nitrate. It 

 would seem that adenine, as well as hypoxanthine, and pos- 

 sibly xanthine, 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 compound containing 

 one molecule of silver nitrate. We have in this behavior 



