262 NITROGEN BASES 



and carefully dried, and then extracted in a Soxhlet extractor 

 with chloroform or carbon tetrachloride ; the extract is then 

 shaken up with dilute sulphuric acid, whereby the sulphate is 

 formed ; the acid layer containing the salt in solution is then 

 run off and evaporated, when the alkaloid salt crystallizes out 

 and can be further purified by recrystallization. 



Example. — Preparation of quinine from cinchona bark. 

 Twenty grams of quicklime are stirred up with 200 c.c. of 

 water and then thoroughly mixed in a mortar with 100 grams 

 of cinchona bark which have been ground up in a coffee mill. 

 The resulting mixture is then dried over a water bath, care 

 being taken to prevent the formation of lumps. The dried 

 substance is then extracted in a Soxhlet apparatus with 

 chloroform. The extract is then shaken up with 25 c.c. of 

 dilute sulphuric acid, the chloroform layer being run off from 

 below ; it is then shaken up with water several times and the 

 water and acid extracts are mixed together and neutralized 

 with ammonia. On evaporating the solution, quinine sulphate 

 crystallizes out; the amount obtained rarely exceeds 1-2 

 grams in weight. 



N.B. — A rapid way of testing a piece of bark for quinine 

 consists in heating it in a dry test tube. If there is any 

 quinine present, the bark will give off a carmine-coloured 

 vapour. 



THE ORIGIN OF ALKALOIDS IN THE PLANT. 



According to Pictet,* alkaloids are produced in the plant 

 in two successive stages, involving (i) the breakdown of 

 complex nitrogenous substances, such as protein or chlorophyll, 

 with the production of relatively simple basic substances ; (2) 

 the condensation of these relatively simple substances with 

 other compounds present in the plant, with the formation of 

 the complex molecules possessed by the alkaloids. 



The processes of metabolism within the plant would there- 

 fore be strictly analogous to those taking place in the animal 

 body, in which waste products, such as phenol, glycine, etc., 

 are coupled up with other substances, such as sulphuric or 

 benzoic acid, before being eliminated. 



* Pictet: "Arch. Sci. Phys. Nat.," 1905, [iv], 19, 329; " Ber. deut. chem. 

 Gesells.," 1907, 40, 3771. 



