356 CHEMISTRY OF THE LEUCOMAINS. 



it forms bright-yellow, very voluminous bunches of long, fine needles 

 which, on drying, acquire a silky luster and form a felted mass. It 

 is difficultly soluble in cold water (1:3500); more readily in hot 

 water and in alcohol (96 per cent.) ; is insoluble in dilute acids. It 

 dissolves readily in a solution of sodium phosphate, from which solu- 

 tion it is precipitated by hydrochloric acid. Other salts of adenin, 

 as the metaphosphate, behave in the same way. Uric acid is also 

 dissolved by sodium phosphate (Wulff). The water of crystalliza- 

 tion is not lost on exposure to air, but is driven off at 100°; the salt 

 then remains unchanged even at 220°. A cold concentrated aqueous 

 solution of the salt treated with one-tenth its volume of cold concen- 

 trated solution of sodium picrate produces a precipitate of short, fine 

 needles, consisting of most of the adenin picrate (five-sevenths). 

 The solubility of the picrate can thus be reduced to as low as 

 1 : 13750, and on this fact is based the quantitative method of 

 Sruhns. The salt can also be obtained in its characteristic groups 

 by combining cold saturated aqueous adenin solution (1 : 1086) with 

 picric acid ; with sodium picrate, however, adenin gives no precipi- 

 tate, since the picrate is soluble in an equivalent quantity of sodium 

 hydrate. Thus is explained Kossel's statement that adenin forms 

 an easily soluble compound with picric acid. Heated on platinum 

 foil it burns slowly and leaves considerable carbon residue. The 

 very bright yellow color of the salt serves to distinguish it from most 

 of the other picrates, especially guanin picrate. Adenin may be iso- 

 lated from its picrate by extraction of the hydrochloric acid solution 

 with ether, by precipitation of the ammoniacal solution with silver 

 nitrate, and best, according to Kriiger, by dissolving the picrate in 

 hot dilute ammonia, and when cold precipitating most of the picric 

 acid with ammoniacal copper sulphate solution. The filtrate can 

 then be evaporated, dissolved in dilute H^SO^, and the last traces of 

 picric acid removed with ether. 



It may be noted that adenin and guanin form difficultly soluble 

 picrates, whereas xanthin and hypoxanthin form relatively easily 

 soluble compounds. 



The platinochlorid, (C5H5N5.HCl)2PtCl^, crystaUizes from dilute 

 aqueous solution in small yellow needles. The concentrated aqueous 

 solution of this salt, when boiled for some time, decomposes, with 

 the separation of a clear, yellow powder, which is but slightly soluble 

 in cold water, and has the composition CjHjNj.HCl.PtCl^ . 



The aurochlorid, on evaporation, yields very characteristic forms. 

 It has been more recently studied by Wulff, and found to possess 

 the formula C5H5N5.(HCl)j,.AuCl3 + B-P. From the hydrochloric 

 acid solution of adenin and gold chlorid, on sufficient concentration, 

 or from dilute solutions by gradual evaporation, it separates in 

 bright, well formed orange-colored crystals, which may attain a 

 length of 1.2 cm. As pointed out by Kossel, this salt is well 



