150 



SOME POISONOUS PLANTS IN N.O. SOLANACEiE, 11., 



of moisture. The whole was distilled as before, in a current of 

 steam, until the alkaloid was completely volatilised. The alka- 

 loid was isolated and purified as in the last case, neutralised 

 with excess of tenth-normal oxalic acid, and the excess deter- 

 mined by titration, using cochineal indicator. The result in 

 this case gave 0*01 78 gm. of alkaloid, or 0015 per cent, of the 

 plant (dried at 100°). 



If we regard the above sample containing 7'2 per cent, of water 

 as a fair average specimen of fresh material, we can express these 

 results also in terms of the green plant, and thereby form a better 

 idea of the amount of alkaloid in the original plant as eaten by 

 stock. The results may then be stated : — 



Amount of Alkaloid expressed as Nicotine. 



Examination of the Alkaloid, — The aqueous solution is alkaline 

 to litmus, and possesses a burning taste, and the characteristic 

 tobacco odour. The pale yellow substance, when exposed to the 

 air, oxidises, and turns dark brown; it then possesses the nause- 

 ating odour of nicotine. 



Of the salts of nicotine, the most characteristic, and the one 

 best adapted for the identification of the alkaloid, is the picrate. 

 Accordingly, the picrate was prepared from the aqueous solution 

 by the addition of excess of picric acid. The dense yellow pre- 

 cipitate, amorphous at first, gradually assumed, on standing, the 

 characteristic, thin, yellow, needle-shaped crystals. At the same 

 time, pure nicotine picrate was prepared under similar conditions, 

 and the crystals compared. Under the microscope, they were pre- 

 cisely alike. The crystals were washed conipletely with distilled 

 water, and recrystallised three times from water, then finally dried 

 at iOO°C. The melting-points were then determined together: — 



Picrate of N. sua veolens alkaloid — ni.p. 218°C. (corrected). 



Picrate of pure nicotine 218 



The two mixed together 218 



The melting-point of nicotine picrate has been determined by 

 Pinner and Wolffenstein as 218°C.(Ber.24, 1891, 66). 



