HANDBOOK FOR BIO-CHEMICAL LABORATORY. 57 



small volume. This is made alkaline with ammonia and 

 allowed to stand, when a deposit of guanin will occur, while 

 the hypoxanthin and adenin (besides ammonium nitrate) 

 remain in solution. Filter off the guanin and wash with 

 water. The filtrate is evaporated to dryness on the water- 

 bath and the residue extracted with small amounts of water 

 to remove the ammonium nitrate, leaving the insoluble hypo- 

 xanthin and adenin. 



Properties. Xanthin is amorphous, or forms masses of 

 crystalline leaves. It is soluble with difficulty in water (in 

 14,151 to 14,600 parts water at -f 16 C. and in 1300 to 

 1500 parts at 100 C.). It is insoluble in alcohol or ether, 

 but is dissolved by alkalies or acids. Xanthin forms a crys- 

 talline, difficultly soluble combination with HC1. With very 

 little caustic soda, xanthin gives a crystalline combination 

 which is readily soluble in more alkali. When dissolved in 

 ammonia, xanthin gives a gelatinous precipitate of xanthin 

 silver, with silver nitrate. This body is soluble in nitric acid. 

 A watery solution of xanthin is precipitated on boiling with 

 copper acetate. Xanthin is precipitated at the ordinary tem- 

 peratures by mercuric chloride and also by ammoniacal basic 

 lead acetate. 



Hypoxanthin occurs as colorless, crystalline needles, which 

 are soluble in 300 parts cold and 78 parts boiling water. It 

 is nearly insoluble in alcohol, but is soluble in acids or alkalies. 

 The combination with HC1 is crystalline, but is more soluble 

 than the corresponding combination with xanthin. The 

 silver combination with hypoxanthin dissolves with great 

 difficulty in boiling nitric acid. Hypoxanthin picrate is diffi- 

 cultly soluble, but if a boiling solution is treated with a neu- 

 tral or faintly acid solution of silver nitrate, the hypo- 

 xanthin is quantitatively precipitated as a combination, hav- 

 ing the formula C b H 3 AgX 4 O.C 6 H a (XO a ) 3 OH. 



Adenin crystallizes with 3 rnol. water of crystallization in 

 long needles, which become opalescent when heated or ex- 



