Peat of Certain Nucleic Acid Derivatives. 41 



autoclave for five hours at 140° C. The prochict was dihited with distilled 

 water to 400 c.c, and hot saturated barium hydroxide added in excess to the 

 boiling solution. This precipitated the sulphuric and phosphoric acids, 

 together with much of the colouring matter. Excess of barium hydroxide 

 was removed by carbon dioxide, and the yellow filtrate concentrated to 

 150 c.c. This was acidified with nitric acid, and silver nitrate added as long 

 as a precipitate formed. This silver-purine precipitate was removed by 

 filtration, and to the cooled filtrate silver nitrate was further added until a 

 drop of cold saturated barium hydroxide produced a yellow precipitate. 

 Barium hydroxide was then added until the solution was permanently 

 alkaline and precipitation ceased. 



(b) Examination of the Silver-Pyrimidine Precipitate. — The precipitate was 

 filtered by means of a pump, suspended in hot water and decomposed with 

 hydrogen sulphide. A trace of barium was quantitatively removed with 

 sulphuric acid, and the filtrate from the silver sulphide concentrated to a 

 small volume. A hot saturated solution of picric acid was then added, but 

 after standing for 48 hours no precipitate of cytosine picrate appeared. The 

 picric acid was therefore extra,cted with sulphuric acid and ether, and, after 

 removal of most of the sulphuric acid by barium hydroxide, the liquid was 

 again concentrated, when fine needle clusters formed. The liquid also gave 

 the pyrimidine colour reaction of Wheeler and Johnson. 



The method of preparation of this substance, its failure to form an 

 insoluble picrate, the needle clusters formed in sulphuric acid solution, 

 together with the Wheeler and J ohnson colour reaction, identify it as uracil. 



(c) Examination of the Silver-Purine Precipitate. — The silver-purine com- 

 pound was suspended in hot water, decomposed with hydrochloric acid, and 

 the precipitate of silver chloride filtered off. A portion of this filtrate was 

 tested for guanine by adding excess of ammonia at the boiling point. As no 

 trace of a precipitate of guanine was obtained, to another portion of the 

 filtrate picric acid was added and a drop or two of ammonia, when a copious 

 precipitate of fine needles at once appeared. This was filtered off and 

 recrystallised from hot water, when the crystals appeared in the form of 

 prisms. These were dried and were found to melt with effervescence and 

 decomposition at 277° C, the melting point of adenine picrate. This 

 substance was further identified as adenine by the characteristic formation 

 of the following salts : the bichromate, as six-sided plates ; the double salt 

 with gold chloride, as long orange coloured prisms ; the hydrochloride, as 

 flat deliquescent prisms. The substance also gave a gelatinous precipitate 

 with ammoniacal silver nitrate, a fine red colour with ferric chloride, 

 unchanged by heating, and responded to Kossel's test for purine bases. 



VOL, xc. — B. E 



