EPISABKIN. 421 



It is difficultly soluble in hot water ; almost wholly insoluble in 

 cold water (1 : 13,000). It is readily soluble in dilute hydrochloric 

 acid, from which, on evaporation, the hydrochlorid crystallizes in 

 easily soluble, pretty needles. The base does not yield an insoluble 

 compound with sodium hydrate, though it is possible that the whet- 

 stone-shaped crystals mentioned above represent an ammonium salt. 

 With silver nitrate it gives a precipitate which is insoluble in nitric 

 acid, easily soluble in ammonia. In other respects the salt resembles 

 that of hypoxanthin. Thus, by boiling with nitric acid (1.1 sp. g.) 

 a crystalline silver nitrate compound forms which probably contains 

 one atom of silver, and on digestion with dilute ammonia yields a 

 silver compound with two atoms of silver — since a part of the epi- 

 sarkin passes into the filtrate and crystallizes out on cooling. The 

 base gives white precipitates with phosphotungstic acid, mercuric 

 chlorid, and ammoniacal lead acetate. 



It is distinguished from adenin and hypoxanthin by its almost 

 complete insolubility in cold water ; from the latter by not being 

 precipitated by picric acid, and by not giving the characteristic ruby- 

 red coloration in the alkalinized filtrate, after reduction with zinc and 

 hydrochloric acid (page 370). From lanthin it is distinguished 

 by the absence of the xanthin reaction ; from hetero- and paraxan- 

 thin by the absence of the insoluble sodium compound ; from guanin 

 and adenin by not clouding at 53°, and by the picric acid reaction. 

 The fact that it is not precipitated by picric acid and is precipitated 

 by ammoniacal lead acetate distinguishes it from epiguanin. 



Kriiger, in 1895, from tea extract isolated a base resembling 

 somewhat episarkin. It difi^ered, however, from the latter in giving 

 with picric acid a very fine crystalline compound. It was more soluble 

 in water, and gave different color reactions. 



Nothing definite can be stated regarding the constitution of epi- 

 sarkin. The formula as given by Balke is open to the objection that 

 the sum of the hydrogen and nitrogen atoms is an odd number. 

 Changing for this reason the number of hydrogen atoms to five, we 

 would then have a compound, C^H^NjO. Such a body may be 

 looked upon as an amino derivative of uracil to which it would 

 bear the same relation that guanin bears to xanthin. This relation- 

 ship to the pyrimidin group would be expressed by the structural 



formula : 



HN— CO 



KH,.^ CJH 



N— CH 



According to this structure episarkin with nitrous acid should 

 yield uracil and on cleavage should give guanidin. Furthermore, 

 it would appear to be derived from guanin. Thymin itself may be 

 looked upon as a cleavage and oxidation product of epiguanin. 



