ABENIN. 347 



With ammoniacal silver solution it gives at once a colorless 

 amorphous precipitate, which is not blackened by boiling or by 

 light. Neutral silver nitrate produces a white precipitate which is 

 soluble in hot dilute nitric acid and separates out on cooling as a 

 white granular or crystalline powder. Ammoniacal zinc solutions 

 precipitate purin, especially on heating, in a fine pulverulent form. 

 Mercuric chlorid gives an amorphous precipitate which on boiling 

 becomes crystalline. Phosphotungstic acid produces an extremely 

 fine precipitate, imparting a milky appearance to the fluid. Tannin 

 produces a colorless flocculent deposit, while bismuth iodid in acid 

 solution yields a red granular precipitate. Potassium iodid, ferro- 

 cyanid and Nessler's solution produce no precipitate. 



With bromin it yields a beautiful yellowish-red, crystalline mass, 

 which dissolves on heating and recrystallizes on cooling. It is very 

 resistant to oxidation and with nitric acid it does not give the 

 murexid reaction. 



The 7-methyl and 9 -methyl purins have also been prepared. Of 

 especial interest is the fact that starting out with methyl uracil, a 

 pyrimidin derivative, Gabriel and Colman* (1901), succeeded in 

 converting it into purin bodies — 6-methyl purin and 6-2-methyl- 

 amido purin. 



The pharmacological action of purin is referred to on p. 345. 



Adeniu, CgH^Nj, was discovered by Kossel in 1885. It was pre- 

 pared synthetically by Fischer ' (1) by treating tri-chlor-purin with 

 ammonia and subsequent reduction of the dichlor-adeniu ; (2) by 

 similar treatment of the methyl derivatives of oxy-di-ohlor-purin. 

 The 7- and 9-methyl adenins were incidentally prepared. 



This base was first prepared from pancreatic glands — hence the 

 term adenin, which is derived from the Greek word ad'^v, meaning 

 a gland. It has since been shown to occur together with guanin, 

 hypoxanthin, etc., as a decomposition product of nuclein, and, there- 

 fore, it may be obtained from all tissues and organs, animal or vege- 

 table, rich in nucleated cells. Accordingly it has been found in the 

 kidneys, spleen, pancreatic, thymus, and lymphatic glands, in beer- 

 yeast, in spermatic fluids, but not in testicles of the steer ; occurs 

 also in tea-leaves. In the latter adenin appears to exist in a pre- 

 formed condition, since it can be extracted without the use of acid 

 reagents (hypoxanthin absent, Kriiger, 1896). Tea-extract yields 

 about 6 grams of adenin per liter (Kriiger). 



The thymus gland, as a prototype of embryonic, highly cellular 

 tissue, yields a considerable amount of adenin, but no xanthin 

 (Inoko) ; that from a calf, for instance, was found by Schindler to 

 contain 0.18 per cent. The thymus nucleinic acid (adenylic acid) 



' BerkhU, 34, 1246, 1256. 

 'Berichte. 30. 2238. 



