186 TOBACCO. 



acid (2*5 per cent.) for several hours on a water-bath, 

 filtered, and the leaves washed with hot 1 per cent, acid 

 till the filtrate was colourless. 



" The filtrate was then either evaporated to a low bulk 

 and extracted with alcohol, to get rid of albuminous 

 matters which interfered with the reaction, or neutra- 

 lized with sodic hydrate and the alkaloid extracted with 

 chloroform, the chloroformic solution being shaken with 

 diluted sulphuric acid as in the ordinary methods of 

 alkaloid extraction. 



" The objection to the first method is that the alcohol 

 has to be driven off before the Mayer's reagent can be 

 added, which is troublesome and lengthens the process. 



" The solution of the alkaloid in excess of sulphuric acid 

 having been obtained, Mayer's reagent was carefully 

 added till no more precipitation was observed, the end 

 of the reaction being ascertained when on filtering 

 some of the nicotine solution into a watch-glass and 

 adding a drop of the reagent, no precipitate was formed. 

 With careful manipulation concordant results were 

 obtained. 



" Other methods tried were as follows : 



" Volumetric method. Ten or more grams of powdered 

 tumbeki were distilled with a solution of sodic or potassic 

 hydrate, the distillate being passed into a known volume 

 of decinormal standard solution of sulphuric acid, and the 

 amount of acid neutralized by the nicotine was determined 

 by a standard decinormal solution of soda and the nicotine 

 calculated. 



" By this method the results obtained were invariably 

 too high owing to an appreciable quantity of ammonium 



