Following is the report of these gentlemen on the chemistry of the subject:—
“Four samples of tumbeki were brought under our notice by Mr. Holmes, Curator of the Museum of the Pharmaceutical Society, being of interest on account of their reported greater strength in nicotine as compared with tobacco. The following are the results of our investigations. We may state that so far as we have been able to ascertain no previous researches have been undertaken on the subject.
“Preliminary Examination.—The presence of an alkaloid was demonstrated on the addition of the usual reagents to the acid infusion.
“Isolation of Alkaloid for Physical Examination.—The powdered tumbeki was placed in a retort with milk of lime and steam passed through it till the distillate was no longer alkaline. Alkaloid in abundance was found in the distillate, which had a distinct odour of nicotine. The distillate was then extracted with ether, and the ether slowly driven off. The residue obtained was a light straw coloured oily liquid of powerful odour, giving off irritating fumes when heated.
“Estimation of Nicotine.—In the estimation of nicotine much difficulty was experienced, owing to imperfect knowledge of the alkaloid, and to the imperfect methods recommended in various papers on the subject. The only method we found reliable was by using a standard solution of Mayer’s reagent, obtained by mixing 13·546 grams of mercuric chloride in solution with 49·8 grams of potassic iodide, in solution, and adding water to make 1 litre.[[D]] One c.c. of this solution represents ·003945 grams of nicotine, the precipitate having the formula C₁₀H₁₆N₂I₂.HgI₂.
“The method we adopted of working with this solution was as follows:—One or more grams of dried and powdered tumbeki were treated with diluted sulphuric 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 neutralized 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.