Nicolas Louis Vauquelin’s Analysis of Green Tobacco
Analysis of the Nicotiana latifolia.
By M. Vauquelin.
translated by D. B. Warden.
Though we cannot doubt that the different methods in the preparation of tobacco modify the principles contained in this plant, it is nevertheless certain that the changes which these principles undergo do not entirely destroy their particular properties; for if this were not so, it is evident that we could also make tobacco of all the herbaceous plants; which is not the case.
We are therefore led to believe that there exists in the Nicotiana a substance, which is not found in the other plants with which it has been attempted in vain to fabricate tobacco.
These considerations induced us to undertake a careful chemical analysis of different kinds of Nicotiana, employed to prepare tobacco, as well as of the tobacco of the different manufactures of France and foreign countries.
In undertaking this research, we thought that some advantage might result from it to the manufactury in the preparation of tobacco; or at least that chemical philosophy might draw from it some principle, with the aid of which it may be possible to give a satisfactory explanation of the changes which have taken place in the materials which enter into the composition of tobacco.
I must here mention that M. Robiquet, a young Apothecary of Paris, who is well informed; and M. Warden, Consul of the United States at Paris, who consecrates, with uncommon zeal, the hours not occupied by the functions of his employment, to the exercise of practical chemistry, have assisted me in this long and laborious analysis.
After having pounded the leaves in a mortar of marble, of the Nicotiana latifolia, they were compressed in a towel to seperate all that was soluble. This operation was repeated three times, adding a small quantity of water.
Altho the vegetable was sufficiently squeezed in the towel, the juice contained a great quantity of green matter in suspension, which was seperated by filtration, by means of Joseph paper. The green matter which remained on the filtre was washed and put aside. We shall speak of it afterwards.
Examination of the filtered juice by reactives.
1o This juice reddened deeply the paper of turnsole: a proof that it contains a free acid.
2o The abundant precipitate formed by the oxalat of ammoniac demonstrates the presence of lime, and consequently of lime calcareous salt.
3o The infusion of gall nuts and mineral acids announce, by their brown and voluminous precipitates, the existence of an animal matter, and particularly of albumine.
4o The temperature increased to 30° of Reaumur in determining an abundant coagulation, confirms what the acids and gall nuts announced.
5o The acetate of lead forms a greyish brown depôt, and very abundant, of which the greatest part1 dissolves in distilled vinegar.
This last precipitate leading us to suspect, in the juice of tobacco, the presence of the malic acid, we precipitated, by means of the acetate of lead, a considerable quantity of this liquor coagulated by the heat: thro this precipitate washed and diluted with water, we passed a current of sulphurate hydrogen gas until there was a small excess.
The object of this operation was to reduce the lead to a sulphure, and by this means, to seperate it from the matter to which it was united. To facilitate the precipitation of the sulphurated lead, and to drive away the superabundance of sulphurated hydrogen, we heated and filtered the liquor.
This liquor thus filtered was carefully evaporated to the consistence of a syrop. In this state it had a very acid taste, reddened deeply the infusion of turnsole, formed with ammoniac and alkohol abundant deposits, which, by announcing the presence of an animal matter, prove that a portion of this substance had been taken off by the lead in its precipitation.
Hoping that the acid contained in this thickened liquor would be soluble in the spirit of wine, and that by this method we might seperate it from the animal matter that held it in dissolution, we treated it warm by this agent at 40°; and as soon as the mixture of these two matters took place, an abundant coagulation was produced: the color of the alkohol was yellow, and it became acid.
This acid alkohol having been gently evaporated, left a yellowish residue, very acid, very soluble in water, not crystallizing, giving with the acetate of lead a whitish precipitate, soluble in distilled vinegar, swelling by heat, and emitting vapors which had the odor of caramel; in short converting itself quickly into an oxalic acid by the action of the nitric acid.
From these properties it is not doubtful that the acid, extracted from the leaves of tobacco by the above mentioned method, is the malic. We shall afterwards make known the matter to which it is united in this plant. As to the animal matter which accompanies it, and which was seperated by alkohol, we shall return to it also in a particular article.
As we had put in the juice of the tobacco an excess of the acetate of lead, for the purpose of seperating all the malic acid, we passed thro this liquor sulpherate hydrogen gas until no more precipitate was formed; then we heated, filtered, and evaporated this liquor to the consistence of a thick syrup
Presuming that it still contained animal matter, we treated it by alkohol, which seperated from it a brownish flocconous matter, whose properties left no doubt of its animal nature.
Having evaporated the alkoholic dissolution with precaution, it left a reddish substance of a very bitter taste, which created in the mouth and throat2 absolutely similar to that which prepared tobacco produces.
After some days there was formed in this substance still liquid small crystals, of a needle form, which seperated by means of a very dephlegmated alkohol, presented all the properties of the nitrat of potash.
The bitter matter divested of the alkohol by its evaporation continued a concentrated acid, which appeared to us to be acetic. This acid having been saturated by potash, and the mixture submitted to distillation, gave a clear liquor, and colorless, of which the bitter taste was the same as that of the entire substance before saturation and distillation. The matter remaining in the retort had almost none of this bitter taste, which proves that what it possessed was entirely volatilized. It appears that this singular substance was combined with the acid that accompanied it, because the latter, before it was saturated with an alkali, was not volatilized.
The principle of which we speak has no smell when dissolved in water, which announces that it is not very volatile. It appears difficult to destroy it; for when mixed with a sufficient quantity of oxygenated muriatic acid it still preserved its acrity after a spontaneous evaporation.
The bitter taste and volatility altogether peculiar to this body seem to evince that it is a principle which belongs exclusively to the genus Nicotiana, and which for this reason is new, since the chemists who have given an analysis of this plant, have not, to our knowledge, spoken of it.
Hence we may conclude that this principle which we find in prepared tobacco, of which we shall treat in another memoir experienced any3 change by the different operations which it has undergone; and consequently that it is not the product of any change which has taken place in the constitution of the materials of the plant.
Second method of obtaining the bitter principle contained in the leaves of tobacco.
Instead of precipitating, by the acetate of lead, the juice of tobacco coagulated by the heat as we have described above, the juice may be evaporated by a gentle heat. When reduced to about ¼ of its volume, it is allowed to cool, leaving it to repose: then it deposits a considerable quantity of the malate of lime under the form of small gritty crystals, which, by exposure to air, become opaque. In concentring the liquor by evaporation, it furnishes new quantities of the same salt: at last when it has acquired such a consistence as no longer permits its saline molecules to reunite, it is treated by alkohol to dissolve the malic and acetic acids which are free, as well as the bitter matter, and an ammonical salt, of which we shall afterwards speak, to obtain apart a portion of the animal matter which the heat could not coagulate, on account of the malic and acetic acids which retained it in dissolution.
This animal matter is really combined with the acids, and owes to them its solubility, seeing that saturating those last by an alkali, it precipitates almost entirely.
The action of the above vegetables is so strong for this animal matter, that if the combination be not sufficiently intimate, and that there remains a little water, the alkohol dissolves a portion of it. But when the mixture of these different substances has been sufficiently concentered, the alkali dissolves only the free acids, the bitter matter, the coloring substance, and the muriat of ammoniac, whilst the animal matter, the malat of neutral lime, the nitrate of potash, and the gum form a residue insoluble in alkohol.
To ascertain whether their bitter principle be volatile, we submitted the alkoholic dissolution to distillation, but the liquid product obtained had none of the products which characterise this principle. Hoping to be more fortunate with the aqueous dissolution, we replaced the alkohol by distilled water, and the result was absolutely the same. The water passed off without taste, the substance remaining in the retort was still as bitter as before.
Having put in this liquor a quantity of potash sufficient to saturate the acids it contains, and having recommenced the distillation, we obtained a liquid product without color, which had then all the acrity of the liquor before distillation, whilst the portion that remained in the retort was almost entirely deprived of it.
This experiment seems to prove that this acrid principle contracts an intimate union with the acids, and that the latter retains it sufficiently to prevent it from being influenced by the expansive force of heat.
If, at the moment when the greatest part of this acrid principle has passed, (which takes place when the matter contained in the retort begins to take the consistence of honey,) we change the recepient, in continuing the distillation, we obtain ammoniac oil, and at the close of the operation muriat of ammoniac, which attaches itself to the upper part of the neck of the retort in the form of sublimate: but if we have put more potash than is necessary to saturate the acids, the acid principle we obtain is mixed with ammoniac, and no ammonical salt is sublimed.
The matter which the alkohol does not dissolve is for the most part formed of an animal substance, which appears very analagous to albumine. This matter divested, by alkohol, of the acids which rendered it soluble in water, ceased entirely to be so. Nevertheless there is so great an abhorrence between this substance and the acids, that it always retains a small portion, if not often washed with boiling alkohol.
Having washed this animal matter with alkohol, it was treated with cold water, to which it communicated a light brown color; and the liquor gives by evaporation crystals of nitrat and muriat of potash in small quantity. The coloring matter which accompanies these salts appears to be of a gummous matter.
The animal substance submitted to distillation gives much carbonat of ammoniac partly crystalised and partly dissolved in water, a thick and jetted oil, charcoal which leaves after combustion a substance of which the greatest part is carbonat of lime, doubtless proceeding from some portions of the malate of lime decompozed.
It follows from the above experiments that the juice of the Nicotiana latifolia contains 1o a great quantity of animal matter of the nature of albumine. 2o A gummous matter in very small quantity. 3o Malat and acetate of lime, with an excess of acid. 4o Nitrat and muriat of potash. 5o Muriat of ammoniac. 6o and lastly, a volatile acid principle without color, and which appears to be of a nature altogether different from all those known in the vegetable kingdom.
It nevertheless appears to us nothing else than a very fine oil, which has a certain degree of volatility,4 the property of dissolving in water, and also in vegetable acids, like the usual volatile. For in treating directly by alkohol dry prepared tobacco in leaves, we obtained independently of the acid principle, a brown and thick oil, which has a similar taste.
It is probable that this oil existed originally in the plant in a state of volatile oil, and by the progress of vegetation and desication of the vegetable, it has been in some sort resinated by the accumulation of carbon. It is nevertheless possible that it owes its acrity to a portion of the volatile principle which is there combined.
At least it cannot be doubted that it is to this acrid principle, and to an oil which we have found in the green and dried leaves of Nicotiana that the prepared tobaccoes owe the greatest part of the properties which distinguish them; for these two substances produce in the mouth, and throat, and nose, the same sensations as prepared tobacco.
In the tobacco which is smoked these sensations are modified by an empyrumatic oil, by a pyroligneous acid, and ammoniac formed during the combustion; but we distinguish besides, in a very sensible manner, those which belong to the substances of which we have spoken. In passing the smoke of tobacco thro’ water, as practised in certain countries in smoking, the odor and taste of these particular substances are more pure and agreeable.
We shall not speak of the insoluble residue, nor of the ligneous part of the leaves of tobacco, because we have found nothing therein which does not exist in other plants. It contains much green resin, a small portion of animal matter, of oxalat and phosphat of lime, of iron, silex, ligneous matter, &c.
In a second memoir we shall present an analysis of the tobacco in leaves, and in powder prepared in different countries, to ascertain the effects of art on this vegetable.
MS (PPAmP: APS Archives, Manuscript Communications); in David Bailie Warden’s hand. Enclosed in TJ to Robert Patterson, 31 Aug. 1809.
Nicolas Louis Vauquelin (1763–1829), experimental chemist, was founding director of the École de Pharmacie de Paris in 1803, served as professor of applied chemistry at the Muséum d’Histoire Naturelle from 1804 until his death, and was longtime professor of chemistry at the Faculté de Medecine. He published over three hundred papers on his experiments, discovered the element chromium, and contributed to the discovery of beryllium. Vauquelin was made a foreign member of the American Philosophical Society in 1811 (DSB description begins Charles C. Gillispie, ed., Dictionary of Scientific Biography, 1970–80, 16 vols. description ends ; APS, Minutes, 18 Jan. 1811 [MS in PPAmP]).
Pierre Jean robiquet was a chemist and professor at the École de Pharmacie (Hoefer, Nouv. biog. générale description begins J. C. F. Hoefer, Nouvelle biographie générale depuis les temps les plus reculés jusqu’a nos jours, 1852–83, 46 vols. description ends , 42:414–5). joseph paper was used to clean microscope lenses. The violet-blue turnsole plant (Crozophora tinctoria) was used to dye paper or linen that acted as a litmus by turning red when exposed to acids. acrity is sharpness in taste, tartness. empyrumatic (empyreumatic) tastes or smells of burnt organic matter (OED description begins James A. H. Murray, J. A. Simpson, E. S. C. Weiner, and others, eds., The Oxford English Dictionary, 2d ed., 1989, 20 vols. description ends ).
1. Manuscript: “parts.”
2. Thus in manuscript.
3. Thus in manuscript, but “no” was probably intended.
4. Manuscript: “volalitility.”
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