THE CHEMICAL COMPOSITION OF THE TOBACCO PLANT
ORGANIC AND INORGANIC MATTERS CONTAINED IN TOBACCO AND THE PARTS THEY
PLAY. ANALYSIS OF VARIOUS TOBACCOS. NICOTINE.
THE CHEMICAL COMPOSITION OF THE TOBACCO PLANT
The tobacco plant when subjected to chemical analysis is found to contain
all or most of the following substances:
_Mineral Bases._ Potash, Lime, Magnesia, Oxides of Iron and Manganese,
Ammonia, Silica.
_Mineral Acids._ Nitric, Hydrochloric, Sulphuric and Phosphoric.
_Organic Base._ Nicotine.
_Organic Acids._ Malic, Citric, Acetic, Oxalic, Pectic and Ulmic.
_Other Organic Substances._ Nicotianin, Green and Yellow Resin, Wax
and Fat, Nitrogenous Substances and Cellulose.
The substances which differentiate tobacco from other plants and form its
chief characteristics are Nicotianin, Nicotine and Malic Acid.
The percentage in which the important substances exist in tobacco is given
below:
Nicotine From 1 to 9%
Malic and Citric Acids From 10 to 14%
Oxalic Acid From 1 to 2%
Resins, Oils and Fats From 4 to 6%
Pectic Acid About 5%
Cellulose From 7 to 8%
Albumenoids About 25%
Ash From 12 to 30%
When tobacco is burned, chemical changes occur; the organic and other
compounds are decomposed. The volatile matters pass off in the smoke if
the combustion is complete, and the mineral ash remains. In ordinary pipe
or other tobacco smoking, however, the combustion is not complete and many
decomposition products remain with the mineral ash.
In tobacco smoke the following can usually be found: Furfurol, Marsh Gas,
Hydrogen Sulphide, Hydrogen Cyanide, Organic Acids, Phenols, Empyreumatic
Oils, Pyridine, Picoline Series and possibly some Nicotine.
The ash left after complete combustion is important, as much of the
smoking qualities of the tobacco depends on its constituents. An average
sample gives the following analysis (in 100 parts):
AVERAGE MINERAL CONTENTS OF TOBACCO ASH
Potash About 27%
Soda About 3%
Lime About 40%
Magnesia About 9%
Sodium Chloride About 9%
Sulphuric Acid About 3%
Silica About 5%
Lime Phosphate About 4%
REMARKS ON SOME OF THE SUBSTANCES FOUND IN TOBACCO
_Nicotine_
Of all the substances found in tobacco, nicotine is the most important.
Nicotine in the pure state is a colorless liquid having a specific gravity
of 1.027. It is an organic base having the chemical formula
C{10}H{14}N{2}. It is extremely acid and burning to the taste, and is a
virulent poison. It easily volatilizes; is inflammable, and is soluble in
water, alcohol, ether and some fixed oils. Nicotine has the characteristic
peculiar odor of tobacco.
The amount of nicotine in tobacco is said to depend on the nature of the
soil in which it is grown; rich, heavy soils and strong nitrogenous
manuring favor the production of a large nicotine content; and light,
sandy soils the opposite.
Moreover the nicotine content depends on the age and development of the
plant.
An investigation by Chuard and Mellet showed nicotine contents of leaves:
In young plants 7 weeks old contained .0324%
In plants 10 weeks old contained .0447%
In plants 13 weeks old contained .4989%
In plants 19 weeks old contained .9202%
The longer the plant is permitted to grow the larger will be its nicotine
content.
Schloessing has made a similar investigation and found that in the same
plant the nicotine content varies from 0.79% when young to 4.32% when
fully matured. Most nicotine is found in the ribs and veins.
H. B. Cox (_American Druggist_ V. 24, 1894, p. 95) investigated the
nicotine contents of various manufactured tobaccos. These were not
"proprietary tobaccos" but samples obtained from different sources at
random. His results are given here:
NICOTINE CONTENTS OF DIFFERENT TOBACCOS
_Nicotine_
Syrian Tobacco leaf (a) .612%
American Chewing Leaf .935%
Syrian Tobacco Leaf (b) 1.093%
Chinese Tobacco Leaf 1.902%
Turkish Coarse Cut 2.500%
Golden Virginia (whole strips) 2.501%
Gold Flake Virginia 2.501%
Navy Cut (light) 2.530%
Light Kentuckian 2.733%
Navy Cut (dark) 3.64 %
Best "Bird's Eye" 3.931%
Cut Cavendish (a) 4.212%
Best Shag (a) 4.907%
Cut Cavandish (b) 4.970%
Best Shag (b) 5.00 %
Algerian Tobacco (a) 8.813%
French Grown Tobacco 8.711%
Algerian Tobacco (b) 8.90 %
The average of a number of samples of Syrian tobacco showed 1 to 2%
nicotine, Manila and Havana 1 to 3%, Virginia and Kentucky from 2 to 7%,
and French tobaccos about 9%.
Most of the nicotine in tobacco becomes volatilized and decomposed during
combustion; a small part, however, may form a solution with the water
which is also one of the combustion products. One of the decomposition
products of nicotine is
_Pyridine_
Pyridine is usually found in tobacco smoke. When condensed it is a
colorless non-oily liquid and is considerably less toxic than nicotine.
Reference will be made later on to the effects of nicotine and pyridine on
the human system.
_Potash_
Potash is important as on its amount depends the burning qualities of the
tobacco. It is sometimes present in the ash to the extent of 30%, being
converted into potassium carbonate by burning. Not only for free burning
is the potash valuable, but also for the better volatilization of the
nicotine and other substances. The more perfect the combustion, the fewer
deleterious compounds are formed.
Chlorides, if present, retard the burning of the tobacco, and hence a
tobacco which contains a high percentage of chloride, even if it is rich
in potash salts, is a poor burning tobacco and therefore faulty. While it
is important that the burning should be free and the volatilization as
perfect as possible, yet the smoker does not want his tobacco to burn too
rapidly. To meet this some manufacturers prepare "slow burning" tobaccos
generally by the addition of some chemical which checks the potash.
The aroma and flavor of the tobacco depend to a great extent on the waxes,
resins and oils, as well as on certain of the organic acids.
REFERENCES
U. S. DISPENSATORY. 1907 (19th Edition).
KISSLING. _The Chemistry of Tobacco._ _Scientific American_ (Supp.) 1905,
Vol. 60, No. 1560.
CHUARD & MELLETT. _Variation de Nicotine dans les differents organes de la
plante de Tabac._ Comp. Rend. Acad. d. Sc. (Paris) 1912. Vol. 155, p. 293.
PEZZOLATO, A. _Conferenza Sulla Chimica applicato alla technologia del
Tabacco._ (Rome. 1903.)
WOLF, JACOB. _Der Tabak und die Tabak fabrikate._ Chapter III. Leipzig,
1912.
SCHLOSSING. _Sur la production de la nicotine par la culture du Tabac._
Compt. Rend. Acad. d. Sc. (Paris), 1910. Vol. 151, p. 23.