220 THE CONSTITUENTS OF PLANTS. IX. 



alcohol. They are found in various parts of plants and may 

 be extracted by digesting the finely divided material with dilute 

 sulphuric acid, nearly neutralising the solution with alkali, 

 boiling down, and adding alcohol, when most of the gums, 

 mucilage, &c., are precipitated and the alkaloids remain in 

 solution. 



Some of the more important alkaloids are 

 Coniine, C 8 H 17 N=propyl piperidine, C 5 H 10 (C ; ,H 7 )N. 



Nicotine, C 10 H 14 N 2 = dipyridyl/^ H:CH ^- CH ( CA )^ H - 

 hexahydride IcH : N. C . N H . CH 2 



Morphine, C 17 H 19 NO :V 

 Strychnine, C 21 H 22 N 2 2 . 

 Quinine, C 2 oH 24 N 2 2 . 



CH 8 .N CH 



Caffeine or Theine, C H H 10 N 4 O 2 = C0 C N.CH 



(Trimethyl xanthine) 



)CO. 



CH,.N C=N' 



Theobromine, C 7 H H N 4 2 



(Dimethyl xanthine) 



CH,.N CH 



I II 

 CO C N.CH* 



>co. 



H.N C=N 



The two latter bodies, though different in constitution from 

 the true alkaloids, are important constituents of certain plants 

 tea (and coffee) and cocoa ; they are intimately connected 

 in chemical constitution with xanthine, C.-,H 4 N 4 2 , found in 

 many animal products and in certain plants ; with guanine, 

 CfiH 5 N 6 0, found in guano (p. 130) ; and with uric acid, C.-,H 4 

 N 4 8 , found in urine. 



The following formulae will illustrate these connections : 



Uric acid. (iuamiie. 



NH CO NH CH 



I I li 



CO C NH X NH=C C NH 



>co 



NH C NH/ NH 



[ C = N 



\co 



