190 XANTHINE. 



red solution with water. The uromelanine will be 

 completely precipitated, leaving the liquid colourless. 

 Allow another portion of the red solution to stand 

 some hours, then mix with water ; a precipitate will 

 be produced, but the liquid will be coloured. 



9. Distil dry uromelanine : a neutral oily distillate 

 will pass over, containing no aniline. Add a drop of 

 mercuric nitrate ; a red colour and precipitate will be 

 produced. 



Uropittine. 1. The matter insoluble in ether (see 

 Omicholine) must be boiled with absolute alcohol and 

 filtered ; the filtrate on cooling will deposit uropittine 

 in granules, which may be purified by again dissolving 

 in alcohol and cooling. 



2. Uropittine is a brown resin, fusing in hot water 

 but insoluble in it, slightly soluble in alcohol, insoluble 

 in ether. 



3. It is more soluble in boiling than in cold alcohol, 

 and is obtained as a resin by evaporation, or as a 

 powder by precipitation with ether or with water. 



4. Dissolve in little ammonia, and add calcium- 

 chloride : a reddish-brown precipitate of uropittine- 

 calcium falls down. 



Xanthine, 5 H 4 N 4 3 . 1. From Calculi. Dissolve a 

 small portion of a xanthine calculus in caustic potash, 

 pass carbonic acid through the solution, and wash the 

 precipitate with water. 



