HTPOXANTSIN. 365 



Adenia-hypoxanthin, C5H5N5 + C^H^Np. — The occurrence of 

 this compound was observed by Kossel, but it was isolated and 

 studied for the first time by Bruhns. It can be prepared by cooling 

 a hot aqueous solution of equal parts of the two bases. At first it 

 is obtained as thick, starch-like, semi-transparent masses, which later 

 in part become white and chalky. By spontaneous evaporation of 

 its solution in very dilute ammonia it forms pearly aggregates of 

 very small radially arranged needles, which contain water of crystal- 

 lization. These effloresce somewhat and lose the water at 100°. 

 The compound is more readily soluble in water than its components, 

 but an exact determination of its solubility is impossible, inasmuch 

 as the separation from hot solutions is not completed for some 

 weeks. Any adenin present can be separated by recrystallization. 

 It forms a distinct crystalline hydrochlorid, which should be borne 

 in mind when examining microscopically for the two bases ; but the 

 combination is loose, since addition of gold chlorid brings down the 

 characteristic gold salt of adenin. Ordinarily it does not form salts 

 with sulphuric or nitric acid, but more often is decomposed by 

 these, so that the difficultly soluble adenin crystallizes out. Once, 

 however, Bruhns obtained a sulphate which differed from the 

 pure adenin and hypoxanthin sulphates. This perhaps explains 

 the observation of Kossel that adenin sulphate forms crystals belong- 

 ing to two systems. The compound can be decomposed into its con- 

 stituents by fractional crystallization of the sulphate or nitrate ; but 

 better by forming the picrates, which are very unequally soluble in 

 water. The existence of this compound undoubtedly explains many 

 of the mistakes and discrepancies concerning the properties of hypo- 

 xanthin, which it resembles more than adenin, and for the same 

 reason, perhaps, adenin was so often overlooked. 



Adenin-theobromin, CjHjNj.CjHjNPj,. — This compound re- 

 sembles the preceding, and was prepared by Kruger (1896) from 

 tea-extract. It is easily soluble in hot, more difficultly in cold 

 water. On recrystallization from water partial decomposition takes 

 place. From aqueous solution picric acid throws down adenin, 

 while theobromin remains in solution. It can be obtained, by crys- 

 tallizing an aqueous solution of equal molecules of the two bases, as 

 fine, long prisms of marked silky appearance. 



Hypoxanthin, CjH^N^, sometimes also known as sarcin or sar- 

 kin, was discovered by Scherer (1850) in splenic pulp and in the 

 muscles of the heart, and was named thus because it contains one 

 atom of oxygen less than xanthin. 



The base has been prepared synthetically by Fischer.^ Thus, tri- 

 chlor purin with alkali yields di-chlor hypoxanthin which on reduc- 



^Berichte, 30,2226. 



