GUANINE. 185 



slightly soluble in water, in 14,151-14,600 parts at 16 C., and in 1300- 

 1500 parts at 100 C. (ALMEN ! ). It is insoluble in alcohol or ether, but 

 is readily dissolved by alkalies and with difficulty by dilute acids. With 

 hydrochloric acid it gives a crystalline, difficultly soluble combination. 

 With very little caustic soda it gives a readily crystallizable compound, 

 which is easily dissolved by an excess of alkali. Xan thine dissolved in 

 ammonia gives with silver nitrate an insoluble, gelatinous precipitate 

 of silver xanthine. This precipitate is dissolved by hot nitric acid, and 

 by this means an easily soluble crystalline double compound is formed. 

 Xanthine in aqueous solution is precipitated on boiling with copper 

 acetate. At ordinary temperatures xanthine is precipitated by mercuric 

 chloride and by ammoniacal basic lead acetate. It is not precipitated 

 by basic lead acetate alone. 



When evaporated to dryness in a porcelain dish with nitric acid, 

 xanthine gives a yellow residue, which turns, on the addition of caustic 

 soda, first red, and, after heating, purple-red. If we place some chlorinated 

 lime with some caustic soda in a porcelain dish and add the xanthine 

 to this mixture, at first a dark-green and then quickly a brownish halo 

 forms around the xanthine grains and finally disappears (HOPPE-SEYLER). 

 If xanthine is warmed in a small vessel on the water-bath with chlorine- 

 water and a trace of nitric acid, and evaporated to dryness, and the 

 residue is then exposed under a bell-jar to the vapors of ammonia, a 

 red or purple-violet color is produced (WEIDEL'S reaction). E. FISCHER 2 

 has modified WEIDEL'S reaction in the following way: He boils the xan- 

 thine in a test-tube with chlorine-water or with hydrochloric acid and a 

 little potassium chlorate, then evaporates the liquid carefully, and moistens 

 the dry residue with ammonia. 



HN CO 



Guanine, C 5 H 5 N. 5 O, = H 2 N.G C NH V (2-amino-6-oxypurine) . 



II II >CH 



N C N^ 



Guanine is found in organs rich in cells. It is further found in the muscles 

 (in very small amounts), in the scales and in the air-bladder of certain 

 fishes, as iridescent crystals of guanine-lime ; in the retinal epithelium 

 of fishes, in guano, and in the excrement of spiders it is found as chief 

 constituent. It also occurs in human and pig urine. Under patholog- 

 ical conditions it has been found in leucsemic blood, and in the muscles, 

 ligaments, and articulations of pigs with guanine-gout. 



Guanine is a colorless, ordinarily amorphous powder, which may be 

 obtained as small crystals by allowing its solution in concentrated ammonia 

 to evaporate spontaneously. According to HORBACZEWSKI it may under 



1 Journ. f. prakt. Chem., 96. 2 Ber. d. deutsch. chem. Gesellsch., 30, 2236. 



