12 BULLETIN 158, U. S. DEPARTMENT OF AGEICULTUEE. 
of a solution of silver nitrate and ammonia. 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. No 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 guanme by means of the xanthine reaction 
and WeideFs test, both of which were positive. From the remainder 
of the solution the characteristic picrate of guanine described by 
Capranica ^ and the dicromate described by Wulff ^ 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 estabhsh the identity of the compound as guanine. 
EypoxantTiine. — 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 resembhng those of hypoxanthine hydro- 
chloric separated out in whetstonehke crystals or bunches of prisms. 
Hypoxanthine forms a characteristic silver nitrate salt^ and a char- 
acteristic silver picrate salt^ both of which are crystaUine and rela- 
tively insoluble in water. Hypoxanthine does not give the xanthine 
reaction, but when treated with nitric acid and bromine water a 
yeUow color is produced which on addition of sodium hydroxide 
turns red, and on heating acts hke the xanthine reaction. . By means 
of these reactions the substance was identified as hypoxanthine. 
THE CHEMICAL CHANGES INVOLVED IN PROCESSING. 
The compounds which were isolated from the base goods are tabu- 
lated in Table IV according to the sources from which they have been 
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 
1 Zeit. physiol. Chem., 4, 233 (1880). 3 Neubauer, Zeit. analyt. Chem., 6, 34 (1867). 
a Ibid., 17, 477 (1893). * Bruns, Zeit. physiol. Chem., 14, 555 (1890). 
