CHEMISTRY OF THK I, K UCOM AI NES. 321 



solubility and ready crystallization (a distinction from the 

 paraxanthine salt). The salt forms large colorless tufts 

 -I' < r\-tal-, \\liidi on contact with water soon lose their 

 transparency and become opaque ; gradually their crystal- 

 line form di. -appears, till Anally tfiey completely decom- 

 pose with the formation of heteroxanthine. This decora- 

 position is hastenetl by warming, either with or without 

 addition of ammonia. Platinum chloride produces in the 

 hydrochloric acid solution a precipitate of crystalline double 

 salt. 



This base resembles paraxanthine in its property of 

 yielding a difficultly soluble precipitate with the fixed 

 alkali. This reaction is best brought al>out by dissolving 

 the heteroxanthine hydrochloride in warm dilute sodium 

 hydrate, when, on cooling, the corresponding sodium salt 

 will crystallize out in oblique-angled plates. These crystals 

 dissolve easily in water, and on neutralization of the 

 solution with an acid a dense pulverulent precipitate of 

 heteroxantliine forms. It can thus be distinguished from 

 paraxanthine, the sodium compound of which, on similar 

 treatment, yields the characteristic crystalline form of the 

 free base. This sodium reaction, therefore, distinguishes it 

 at once from xanthine, hypoxanthine, guanine, and para- 

 xanthine. It differs from the latter, as has already been 

 indicated, in the solubility and amorphous character of the 

 free base ; in the behavior of the hydrochloride and the 

 sodium compound, and in the not giving a precipitate with 

 picric acid, nor the characteristic odor given by paraxan- 

 thine on heating. 



In its composition, hetero xanthine is, as has already 

 been stated, methvl-xanthhu 1 and probably is related to if 

 not identical with an isomeric body obtained synthetically 

 by GAUTIEB (see page 314). The fact nevertheless re- 

 mains, that in the nrin we have normally a homologous 

 series of xanthine bodies, namely, xanthine, hcteroxanthine, 

 and paraxanthine. 



I'M: \ XANTHINE, C 7 H 8 N 4 O 2 , was isolated in 1883 by 

 SALOMON, who has since shown it to IK; a constituent of 



