ADENIN. 355 



aqueous solution in two different crystalline forms. This may pos- 

 sibly be due to the presence of the adenin-hypoxanthin compound 

 (Bruhns). It is easily soluble in hot water, and at the ordinary 

 temperature it is soluble in 153 parts of water (156, Fischer). 



The oxalate, CjHjNj.CjHjO^ + H^O, is obtained by dissolving 

 adenin in hot, dilute, aqueous oxalic acid, from which solution, on 

 cooling, it separates as a voluminous difficultly soluble precipitate of 

 roundish masses which are composed of long, delicate needles. The 

 oxalates of guanin, hypoxanthin, and xanthin are more easily soluble 

 than that of adenin, and exhibit, moreover, a different appearance. 



Adenin bichromate, (QJi.^^^S.fif)^ . This compound separates 

 in a few hours from a mixture of adenin and chromic acid solutions 

 in well formed yellowish-red crystals (Bruhns). According to 

 Kriiger, it forms six-sided plates, is easily soluble in hot water, diffi- 

 cultly in cold, and is unchanged by heating to 150°. The corre- 

 sponding salt of guanin readily dissociates. 



Adenin metaphosphate, CjHjNj.HPOj. According to Kossel, 

 adenin is not precipitated with metaphosphoric acid, but this is not 

 strictly true. Aqueous, or even cold saturated solutions of adenin give 

 on the addition of a few drops of metaphosphoric acid an amorphous 

 precipitate, appearing under the microscope as fine round granules or 

 extremely thin membranous masses. It has not been obtained in a 

 crystalline condition. Like the corresponding guanin compound, it is 

 difficultly soluble in cold water. It is easily soluble in alkalis and in 

 ammonia ; is more or less soluble in dilute acids according to the con- 

 centration, and is soluble in excess of metaphosphoric acid. Hence 

 a strongly acid, not too concentrated, solution of adenin is not pre- 

 cipitated (Wulff). Adenin is precipitated less completely than 

 guanin, whereas hypoxanthin does not give a difficultly soluble 

 metaphosphate. 



The chloracetate, CjHjNj.ClCHj.COjH, was prepared by Kriiger 

 by adding an excess of chloracetic acid to a hot aqueous solution of 

 adenin. On cooling it crystallizes in right-angled plates and in stel- 

 late four-sided prisms. It is easily soluble in water and in hot 

 aqueous alcohol; difficultly in cold alcohol. At 162°-163° it 

 melts, giving off hydrochloric acid and forming a yellowish-red fluid 

 which gradually becomes intensely red. 



Potassium ferro- and ferricyanid produce no precipitate in a solu- 

 tion of adenin, but if acetic acid is then added the former gives 

 rise to a precipitate of thin plates ; the latter, to a precipitate of 

 light-brown crystals grouped in bunches (Kriiger). According to 

 Bruhns, adenin gives with potassium ferricyanid brownish-green 

 needles. 



The picrate, C5H5]S'5.C5H2(]SrOj)30H + H^O, is thrown down as a 

 bright-yellow flocculent precipitate when aqueous solutions of adenin 

 salte are treated with sodium picrate. Eecrystallized from hot water 



