816 BACTERIAL POISONS. 



and sodium liydrate in a watch-glass the solution becomes 

 covered by a dark-green scum, which changes to a brown, 

 and soon disappears — distinction from hypoxanthine. 



By means of a very interesting synthetic reaction, xan- 

 thine may be converted into theobromine, the active con- 

 stituent of Theobroma cacao. Thus, the xanthine is dissolved 

 in a sufficient quantity of sodium hydrate, necessary to form 

 the neutral compound CjHjN'ajN^Oj, and this product, 

 when treated with boiling acetate of lead, yields a white 

 precipitate of lead xanthine, 05H2PbN40j. This is dried 

 at 130°, then heated for twelve hours at 100° with methyl 

 iodide, when the dimethyl derivative, C^'H2{CIlj)^fij, is 

 formed. This compound is identical with the natural theo- 

 bromine, and by a similar treatment is converted into tri- 

 methyl-xanthine or caffeine. The relation of xanthine to 

 theine (caffeine) is shown in the fact that it exists together 

 with hypoxanthine, adenine, and possibly guanine, in fresh 

 tea-leaves. It is, therefore, clear, that by starting from 

 guanine of guano we can produce successively xanthine, 

 dimethyl xanthine, and trimethyl xanthine, the last two 

 compounds being identical with the alkaloids of theobroma 

 and of coffee. 



iN'asceut hydrogen converts this base into hypoxanthine, 

 but the reverse operation, the oxidation of hypoxanthine 

 into xanthine, has been questioned of late by Kossel and 

 others. On heating, a small portion volatihzes; the 

 greater part decomposes into ammonium carbonate, cyan- 

 ogen, and hydrocyanic acid. Heated to 200° with hydro- 

 chloric acid, it decomposes with the formation of ammonia, 

 carbonic acid, formic acid, and glycocoll (E. Schmidt). 

 When bromine is allowed to act on xanthine, there is 

 formed a substitution compound, having the formula 

 CjHgBrN'^O^. With potassium chlorate and hydrochloric 

 acid it yields alloxan and urea. 



Xanthine is a weak base, which dissolves in acids with 

 the formation of salts. 



The hydrochloride, CsH.K.O^.HCl, is difficultly soluble 

 in water, more so than the corresponding salt of hypoxan- 

 thine, from which it is deposited in glistening six-sided 



