EPIOUANIN. 387 



renals would seem to indicate the existence of di- or trimethyl deriva- 

 tives of guanin in the body as products of nuclein metabolism. A 

 1-7 dimethyl guanin for example might give rise to epiguanin, which 

 in turn would yield heteroxanthin (7-methyl xanthin). Similarly 

 a 1 -methyl guanin is possible, which apparently is the source of 

 1-methyl xanthin. Finally paraxanthin (1-7-dimethyl xanthin) may 

 in part be directly derived from the corresponding guanin derivative. 

 Additional light upon the origin of epiguanin has been gained by 

 the observation of Fischer (1898), that it arises from an adenin 

 derivative apparently by intramolecular migration. 



The natural as well as the synthetic base is precipitated from 

 concentrated solution of its salts by addition of ammonia and imme- 

 diate cooling as whetstone-shaped crystals. Heated rapidly in a 

 capillary it begins to color at about 390° and later chars without 

 melting. The 1-7-dimethyl guanin melts without decomposition at 

 338°- 340° (Fischer). Similar crystals are given by Balke's 

 episarkin, which in many other respects resembles epiguanin. Epi- 

 sarkin, however, is not precipitated by picric acid, but is thrown 

 down by mercuric chlorid and by ammoniacal lead acetate; nor does 

 it give the xanthin reaction. From solutions in sodium hydrate it 

 is precipitated by acids in the form of splendid, matted silky prisms 

 which if agitated in water give a peculiar asbestos-like appearance. 

 The whetstone-like forms on recrystallization from water yield the 

 prismatic type. 



It is difiBcultly soluble in hot water and in ammonia ; almost in- 

 soluble in alcohol and in cold water, a fact which is of value in the 

 isolation of the base. The solubility in boiling water is 1 to 900 

 (Fischer). It is easily soluble in dilute alkali and in hydrochloric 

 and sulphuric acids, difficultly in dilute nitfic acid from which the 

 nitrate separates on cooling in polyhedric crystals. The sulphate 

 forms fine bent needles, which quickly change to elongated often 

 six-sided plates. From 33 per cent, sodium hydrate solution on 

 cooling it crystallizes, probably as a sodium compound, in broad, 

 glistening pointed needles. Carbonic acid precipitates the free base 

 from its solution in dilute alkali (Fischer). 



The picrate, C^^p.C^^l^O^piL, is difficultly soluble in 

 water and is useful tor the identification of epiguanin. It forms a 

 voluminous precipitate which consists of anhydrous, peculiarly bent 

 prisms arranged in fan-like bundles, or of rhombic or six-sided 

 plates. At 18° it is soluble in 2708-2732 parts of water (Kriiger 

 and Salomon); at 16° it is 1 to 3049. It begins to sinter at about 

 253° and decomposes suddenly with evolution of gas at 267°. 

 From a slightly alkaline, warmed solution of the picrate the free 

 base is precipitated at once upon the addition of ammonium chlorid. 



The platinochlorid crystallizes from concentrated solution in long 

 glistening, six-sided orange-colored prisms which on warming with 



