rKESIDENTIAL ADDRESS — SKCTloN li. 53 



reciuired. For the subseciuent distillation in steam, a cupper 

 vessel of about two gallons' cai)acif\r is needed. The distillate 

 and the residual aqueous liquid left in the distilling vessel have 

 to be repeatedly extracted with various organic solvents, and 

 for this purpose a mechanically-driven shaking machine must 

 be used. Some of the apparatus can, of cotirse, be improvised, 

 hut even so the purchase of the remainder is an item which can- 

 not be easily met out of the ordinary grants available for the 

 maintenance of college laboratories. In addition, many gallons 

 of organic solvents, alcohol, ether, chloroform, petroleum ether, 

 etc., are used in the numerous extraction processes. There are 

 several research grants in existence, the money for which is sup- 

 plied mainly by the Government. In order to deal efficiently 

 with the problem under discussion, the number of these grants 

 should be considerably increased. The administration of them 

 should, however, be left, as hitherto, in the hands of the Royal 

 Society of SotUh Africa, or it might perhaps be entrtisted to a 

 Committee of the Associated Scientitic Societies of the country. 

 A preliminary examination of a small ((uantity of material 

 (say 50 grams), according to the modified Dragendorff or Stas 

 Otto method, supplemented by micro-chemical tests on sections, 

 often gives a valuable orientation as to the presence or absence 

 of certain imjx>rtant constituents, such as alkaloids, glucosides, 

 or bitter principles, and may even afford a clue as to their nature. 

 It is impossible to lay down any general law applicable to the 

 treatment of every plant. But, except in the case of plants 

 proved in the preliminary investigation to contain an alkaloid, 

 the following method will, in most cases, lead to results. The 

 material is initially extracted by continuous percolation with hot 

 alc<:)hol, and, after the removal of the greater ])art of the 

 solvent, the extract is subjected to distillation in steam. The 

 distillate, containing essential oils and volatile acids ( formic, 

 acetic, propionic, benzoic), can in most cases be discarded. Tlie 

 aqueous liquid in the distillation flask is separated from the 

 resin, and the two treated se])arately with different solvent-^ or 

 precipitants. The aqueous liquid is usually extracted with ether 

 and amyl alcohol, occasionally also with chloroform, and is 

 finally precipitated with basic lead acetate. The resin is ex- 

 tracted in turn with ])etroleum ether, ether, chloroform, ethyl 

 acetate, and alcohol. Each of the extracts usually contain 

 several substances in solution which, in the case of solvents 

 immiscible with water, may be separated by shaking the extracts 

 wnth aqueous solutions of ammonium carbonate, alkali car- 

 bonate, or hydrates. The substances so obtained can usually 

 be purified bv crystallization or distillation, or both, or if the 

 substances are resinous, acid or alkaline, hydrolysis may result 

 in the formation of crystalline products. IMants ontaining 

 alkaloids may be subjected to a preliminary treatment with a 

 very dilute alcoholic or aqueous solution of a very weak acid 

 (tartaric), which will in most cases remove the alkaloid as a 

 salt. 



