ALKALOIDS 



37 



Although the majority of the alkaloids contain oxygen in their 

 composition, some, e.g.^ nicotine and conine, are free from this 

 element, and these are usually liquid, while the others are solid 

 crystalline substances. 



In the plants in which they occur, the alkaloids are generally 

 found in largest amount in the seeds or the leaves. 



Being secondary or tertiary amines, they are all basic in character, 

 and combine with acids to form salts, and it is often in the state 

 of salts that the alkaloids exist in plants ; they are generally 

 optically active, although a few — piperine, for example — have no 

 action upon the plane of polarisation of light. 



A few of the more important alkaloids, and the plants in which 

 they occur, and their distribution in the plant, are given here- 

 with : — 



Alkaloid. 



Quinine . 

 Nicotine . 

 Strychnine 

 Conine . 

 Caffeine . 

 Piperine . 

 Atropine . 

 Cocaine . 

 Morphine 



Plant. 



Cinchona . 



Tobacco . 



Nux vomica be;in 



Hemlock . 



Tea, coflFee 



Pepper 



Deadly nightshade 



Coca plant 



Poppy (special varieties) 



Greatest Proportion 

 of Alkaloid in 



Bark 



Leaves 



Seeds 



Seeds 



Leaves 



Seeds 



Seeds, leaves 



Leaves 



Seed capsules 



The extraction of the alkaloids and their methods of estimation 

 differ greatly, but in order to give some idea of the processes, the 

 extraction of caffeine from tea and the estimation of nicotine 

 in tobacco leaves are given below. 



21. 



Extraction of Caffeine from Tea, 



A hundred and fifty grams of tea are boiled with 

 about 700 C.C. water for a quarter of an hour, and the 

 infusion is then filtered through unsized calico into 

 a large porcelain basin or beaker. The leaves remain- 

 ing on the cloth are then thoroughly washed with 300 

 c.c. boiling water, the washings being allowed to run 

 into the liquid already obtained. The resulting liquid 



C 2 



