12 BULLETIN 158, U. S. DEPABTMENT OF AGRICULTURE. 



of a solution of silver nitrate and a mm onia. After washing with 

 water the silver precipitate was boiled with 10 c. c. of nitric acid, 

 specific gravity 1.1, and filtered. From this solution, on cooling and 

 standing, crystals were deposited which were filtered off. 



The filtrate was diluted with water, made alkaline by the addition 

 of ammonia, and a solution of silver nitrate added. Xo precipitate 

 was formed showing the absence of xanthine. 



Guanine. — The precipitate from the nitric acid solution was washed 

 with water, suspended in water, and decomposed with hydrogen 

 sulphide. The solution was filtered and concentrated to about 

 10 c. c. when strong ammonia was added producing a white gelatinous 

 precipitate which was filtered off and washed with a little cold water. 

 The precipitate was dissolved in a little warm hydrochloric acid and 

 tested for the presence of guanine by means of the xanthine reaction 

 and TTeidel's test, both of which were positive. From the remainder 

 of the solution the characteristic picrate of guanine described by 

 Capranica 1 and the dicromate described by WuifT 2 were prepared. 

 The method of obtaining this base, its solubility in water, ammonium 

 hydroxide, and hydrochloric acid, the solubility of the silver salt in 

 nitric acid, specific gravity 1.1, the color reactions, and the formation 

 of the two characteristic salts, the picrate and dichromate, are suffi- 

 cient to establish the identity of the compound as guanine. 



Hypoxanihine. — The filtrate from the ammonia precipitation of 

 guanine was boiled to expel all the ammonia and to a portion of the 

 solution a solution of picric acid was added, but no precipitate was 

 immediately formed, showing the absence of adenine. To another por- 

 tion of the solution hydrochloric acid was added and the solution was 

 concentrated when crystals resembling those of hypoxanthine hydro- 

 chloric separated out in whetstonelike crystals or bunches of prisms. 

 Hypoxanthine forms a characteristic silver nitrate salt 3 and a char- 

 acteristic silver picrate salt 4 both of which are crystalline and rela- 

 tively insoluble in water. Hypoxanthine does not give the xanthine 

 reaction, but when treated with nitric acid and bromine water a 

 yellow color is produced which on addition of sodium hydroxide 

 turns red, and on heating acts like the xanthine reaction. By means 

 of these reactions the substance was identified as hypoxanthine. 



THE CHEMICAL CHANGES INVOLVED LN PROCESSING. 



The compounds which were isolated from the base goods are tabu- 

 lated in Table IV according to the sources from which they have beeD 

 derived and the chemical groups to which they belong. While it was 

 not possible to isolate these compounds in a strictly quantitative 

 manner, nevertheless it was evident that the purine bases were 



i Zeit. physiol. Chem., 4, 233 (1880). a Xeubauer, Zeit. analyt. Chem., 6, 34 (1867). 



2 Ibid., 17, 477 (1893). * Brans, Zeit. physiol. Chem., 14, 555 (1890). 



