CHEMISTRY OF THE LEUCOMAINES . 325 



acid, from which on cooling it separates in white crystalline 

 tufis possessing a silijy lustre. On decomposition with 

 hydrogen sulphide the silver salt yields pure paraxanthine. 

 Picric acid produces in the hydrochloric acid solution a 

 precipitate consisting of densely felted yellow crystalline 

 spangles. 



It is also precipitated by phosphotungstic acid and copper 

 acetate; mercuric chloride when added in excess gives a 

 precipitate composed of a mass of colorless prisms, which 

 are rather difficultly soluble in cold water ; easily in hot 

 water. The crystals of paraxanthine mercuric chloride 

 when moderately heated become opaque from loss of water 

 of crystallization ; at a higher temperature they melt, under- 

 going at the same time partial decomposition, and on strong 

 heating they evolve disagreeable nauseatiug vapors. The 

 aqueous solution of this mercuric double salt gives with 

 silver nitrate an abundant precipitate of silver chloride, 

 which disappears on the addition of ammonium hydrate 

 and is replaced, by the flocculent gelatinous precipitate of 

 silver paraxanthine. The hydrochloric acid solution of 

 paraxanthine crystallizes with difficulty even when strongly 

 concentrated, and on the addition of platinum chloride it 

 yields a well-crystallizable orange-colored paraxanthine 

 platinochloride. It is not precipitated by basic lead acetate 

 nor by mercuric nitrate. 



In its behavior to the xanthine test this base resembles 

 hypoxanthine, whereas in giving Weidel's reaction it 

 approaches xanthine. Finally, it coincides with guanine 

 by yielding a precipitate with picric acid. Although it 

 thus agrees in some of its reactions with all three of these 

 xanthine bodies, it can, however, be easily distinguished 

 from them by its behavior with the fixed alisalies. Sodium 

 or potassium hydrate dissolves these bases and holds them 

 in solution, but when added to concentrated paraxanthine 

 solution the alkali produces a precipitate of long, glittering, 

 crystalline spangles, which under the microscope are seen to 

 consist of delicate rectangular, often longitudinally striated, 

 plates which are either isolatea or united in tufts. Besides 

 these crystals there are also present hexagonal plates resem- 



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