28 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



solution as long as a precipitate is formed, filter, and remove 

 the excess of lead from the filtrate with hydrogen sulphide. 

 Boil the solution or concentrate it on the water-bath, in 

 order to get rid of the excess of hydrogen sulphide, make 

 strongly alkaline with ammonia, and precipitate with an 

 ammoniacal solution of silver nitrate, etc., etc. 



The hypoxanthine (or sarcine), C 5 H 4 N 4 0, is very diffi- 

 cultly soluble in cold water (in 1400 parts at 19), somewhat 

 more soluble in hot water (70 parts). It dissolves readily in 

 mineral acids, forming well-crystallized salts, and in alkalies, 

 even in ammonia (distinction from guanine, which is but 

 very slightly soluble in ammonia). It gives the so-called 

 xanthine reaction, but less markedly than any of the other 

 xanthine bases. 1 



Reactions of Hypoxanthine. 



1. Pour upon a small portion of the substance on a por- 

 celain crucible cover a few drops of strong or fuming nitric 

 acid and evaporate cautiously to dryness over a small flame. 

 A lemon-yellow residue results, which takes on an orange 

 color when moistened, after cooling, with caustic soda solu- 

 tion. If a drop of water be then added, a yellow solution 

 results, and this when evaporated again leaves an orange 

 residue (distinction from the murexide reaction for uric acid). 



2. Pour upon a small portion of the substance in a dish a 

 little pure nitric acid of the specific gravity 1.2, and evaporate 

 on the water-bath to dryness. The residue is scarcely per- 

 ceptibly colored. On the addition of caustic soda it becomes 

 pale yellow (distinction from xanthine and guanine, which 

 under these conditions give the xanthine reaction). Hypo- 

 xanthine is further distinguished by its solubility in ammonia 



1 According to Hoppe-Seyler, Thierfelder, 7th edition, page 147, hypo- 

 xanthine does not give the xanthine reaction.- 



