3. That it is sufficiently easy to prove its presence in the liver and the other organs, after it has been absorbed.
1. Pure Nicotine may be characterised as easily as a Poison derived from the Mineral Kingdom.—Nicotine, discovered in 1809 by the illustrious Vauquelin, was studied in 1828 by Messrs. Posselt and Reimann, who found it in different species of nicotiana, in macrophylla rustica, and glutinosa. Messrs. Boutron, Charlard, and Henry described some of its properties in 1836. Havanna tobacco contains two per cent., that of Maryland 2·3, that of Virginia 6·9, that of Alsace 3·2, that of Pas-de-Calais 4·9, that of the Nord 6·6, and that of Lot 8. It is classed among the natural volatile vegetable alkalies, which are only three in number, namely, conicine, theobromine, and nicotine. This last is entirely composed of hydrogen, carbon, and nitrogen. It may be represented as a compound of one equivalent of ammonia (H3N), and of one of a hydro-carbon containing four equivalents of hydrogen and ten of carbon (H4C10). It is now obtained by a much more simple process than was formerly adopted, which consists in passing the vapor of tobacco into water acidulated with sulphuric acid. Sulphate of nicotine is thus speedily produced, and this has to be decomposed by a strong alkali. It is then only necessary to apply sufficient heat to volatilize the nicotine. This mode of preparation indicates that smokers in respiring the smoke of tobacco introduce into their bodies a certain quantity of the vapor of nicotine.
Characters of pure Nicotine.—It is in the form of an oleaginous, transparent, colorless, tolerably fluid, anhydrous liquid, of the density of 1·048, becoming slightly yellow with keeping, and tending to become brown and thick from contact with the air from which it absorbs oxygen; its acrid odor resembles but slightly that of tobacco; its taste is very burning. It volatilizes at 77° F., and leaves a carbonaceous residue. The vapor which rises presents such a powerful smell of tobacco, and is so irritating, that it is difficult to breathe in a room in which one drop of it has been spilt. If this vapor be approached with a lighted taper, it burns with a white smoky flame, and leaves a carbonaceous residue as an essential oil would do. It strongly blues reddened litmus paper. It is very soluble in water, in alcohols, and in fat oils, as also in ether, which easily separates it from an aqueous solution. The great solubility of nicotine in both water and ether forms an important fact in its chemical history, as the greater number of vegetable alkalies, not to say all, if they dissolve easily in one of these liquids, are not readily soluble in the other. {19}
Nicotine combines directly with acids, disengaging heat. Concentrated pure sulphuric acid, without heat, produces with it a wine-red color; on the application of heat to this it becomes thick, and acquires the color of the dregs of wine; if it be boiled it blackens and disengages sulphurous acid. With cold hydrochloric acid it disengages white vapors as ammonia does; if the mixture be heated it acquires a violet color, the intensity of which increases with prolonged ebullition. Nitric acid, aided with a little heat, imparts to it an orange-yellow color, and white vapors of nitric acid are first given off, then red vapors of hyponitrous acid. If it be further heated the liquor becomes yellow, and by ebullition it acquires a red color resembling that of chloride of platinum. Prolonged ebullition gives a black mass. Heated with stearic acid it dissolves and forms a soap, which congeals on cooling, and is slightly soluble in water, and very soluble in heated ether. The simple salts of nicotine are deliquescent, and difficultly crystallizable. The double salts which it yields with the different metallic oxides crystallize better.
The aqueous solution of nicotine is colorless, transparent, and strongly alkaline. It acts like ammonia on several reagents; thus, it gives a white precipitate with bichloride of mercury, acetate of lead, protochloride and bichloride of tin; a canary yellow precipitate with chloride of platinum, which precipitate is soluble in water; a white precipitate with salts of zinc, which is soluble in excess of nicotine; a blue precipitate with acetate of copper. This precipitate is gelatinous and soluble in excess of nicotine, forming a blue double acetate, similar to that formed by ammonia with the same salt. It gives an ochre-yellow precipitate with salts of the sesqui-oxide of iron, insoluble in excess of nicotine. With sulphate of protoxide of manganese it gives a white precipitate of oxide, which speedily becomes brown by contact with the oxygen of the air. It separates the green sesqui-oxide from the salts of chromium. The red permanganate of potash is instantly decolorized by nicotine, as by ammonia, although this latter alkali acts more slowly and must be used in larger proportion.
The following reactions may serve to distinguish the aqueous solutions of nicotine from ammonia. Chloride of gold yields a reddish-yellow precipitate, very soluble in an excess of nicotine. Chloride of cobalt yields a blue precipitate, which changes to green; the oxide thus formed does not readily dissolve in excess of nicotine, whilst ammonia dissolves the green precipitate and forms a red solution. Aqueous solution of iodine gives a yellow precipitate with solution of nicotine, as chloride of platinum would {20} do; with an excess of nicotine it acquires a straw color, and it is decolorized by the action of heat. Ammonia, on the contrary, immediately decolorizes the aqueous solution of iodine without rendering it turbid. Pure tannic acid gives with nicotine an abundant white precipitate. Ammonia gives no precipitate, but imparts a red color.[4]
[4] It is interesting to compare the physical and chemical properties of nicotine with those of conicine.
Conicine is yellow; its smell resembles that of the urine of the mouse, and differs entirely from that of nicotine; it strongly blues reddened litmus paper. Added to water and shaken with it, it floats on the surface and is not readily dissolved. Ether dissolves it easily. When heated in a capsule it forms white vapors, having a strong smell of celery mixed with that of the urine of the mouse. Weak tincture of the iodine yields a white precipitate, which acquires an olive color with excess of the tincture. Pure and concentrated sulphuric acid does not alter it; when the mixture is heated it acquires a greenish brown color, and if the heat be continued it becomes blood-red and afterwards black. Nitric acid imparts to it a topaz color, which is not changed by the action of heat. Hydrochloric acid yields white vapors as ammonia does, and renders it violet, especially when heated. Tannic acid gives a white precipitate, and chloride of platinum a yellow precipitate. The red permanganate of potash is immediately decolorized. Corrosive sublimate yields a white precipitate. Acetate of copper gives a gelatinous blue precipitate, less soluble in an excess of conicine than is that formed with nicotine. Chloride of cobalt behaves with it as it does with nicotine. Chloride of gold gives a light yellow precipitate. Neutral acetate of lead does not give any precipitate; neither does the subacetate. Chloride of zinc gives a white gelatinous precipitate soluble in excess of the conicine. Sulphate of sesquioxide of iron gives a yellow precipitate. The words in italics indicate the means of distinguishing conicine from nicotine.
If to these chemical characters which permit one so easily to distinguish nicotine, we add those resulting from the action which it exercises on the animal economy, it will no longer be possible to confound it with any other body. The following are the results of the experiments I undertook in 1842 on this alkali, and which I published in 1843. (See the 4th edition of my work on Toxicology.)
First Experiment.—I applied three drops of nicotine on the tongue of a small but sufficiently robust dog; immediately afterwards, the animal became giddy, and voided urine; at the end of a minute, its breathing was quick and panting. This state lasted for forty seconds, and then the animal fell on its right side, and appeared intoxicated. Far from showing any stiffness or convulsions, it was feeble and flabby, although the fore paws slightly trembled. Five minutes after the administration of the {21} poison, he uttered plaintive cries, and slightly stiffened his neck, carrying his head slightly backwards. The pupils were excessively dilated; the respiration was calm, and in no way accelerated. This state lasted ten minutes, during which the animal was not able to stand. From this time the effects appeared to diminish, and soon after it might have been predicted that they would speedily disappear entirely. Next day, the animal was quite well. The nicotine I used was evidently not anhydrous.