597. Acid and Basic Constituents of Tobacco.—In unfermented and fermented tobacco are found certain organic acids, among the most important of which are citric, malic, oxalic, pectic and tannic. Of the inorganic acids the chief which are found are nitric, sulfuric and hydrochloric. Among the bases ammonia and nicotin are the most important. Ammonia is found in the unfermented tobacco in only small quantities, but in the fermented product it may sometimes reach as high as half a per cent. The presence of these two nitrogenous bases in tobacco renders the estimation of the proteid matter contained therein somewhat tedious and difficult.
598. Composition of Tobacco Ash.—The mineral constituents of tobacco are highly important from a commercial point of view. The burning properties of tobacco depend largely upon the nature of its mineral constituents. A sample containing a large quantity of chlorids burns much less freely than one in which the sulfates and nitrates predominate. For this reason, the use of potash fertilizers containing large amounts of chlorin is injudicious in tobacco culture, the carbonates and sulfates of potash being preferred. The leaves of the tobacco plant contain a much larger percentage of mineral constituents than the stems, their respective contents of pure ash, that is ash free from carbon dioxid, carbon and sand, being about seventeen and seven. The pure ash of the leaves has the following mean composition: Potash 29.1 per cent, soda 3.2 per cent, lime 36.0 per cent, magnesia 7.4 per cent, iron oxid 2.0 per cent, phosphoric acid 4.7 per cent, sulfuric acid 6.0 per cent, silica 5.8 per cent, and chlorin 6.7 per cent.[616]
599. Composition of Tobacco.—The mean composition of some of the more important varieties of water-free tobacco is shown in the following table:[617]
| Havana, per cent. | Sumatra, per cent. | Kentucky, per cent. | Java, per cent. | |
|---|---|---|---|---|
| Nicotin | 3.98 | 2.38 | 4.59 | 3.30 |
| Malic acid | 12.11 | 11.11 | 11.57 | 6.04 |
| Citric acid | 2.05 | 2.53 | 3.40 | 3.30 |
| Oxalic acid | 1.53 | 2.97 | 2.03 | 3.38 |
| Acetic acid | 0.42 | 0.29 | 0.43 | 0.22 |
| Tannic acid | 1.13 | 0.98 | 1.48 | 0.51 |
| Nitric acid | 1.32 | 0.60 | 1.88 | 0.23 |
| Pectic acid | 11.36 | 11.88 | 8.22 | 10.13 |
| Cellulose | 15.76 | 10.59 | 12.48 | 11.82 |
| Ammonia | 0.49 | 0.06 | 0.19 | 0.23 |
| Soluble nitrogenous matter | 7.74 | 8.84 | 13.90 | 10.39 |
| Insoluble”” | 9.75 | 7.97 | 8.10 | 9.53 |
| Residue and chlorophyll | 5.15 | 8.63 | 1.99 | 6.45 |
| Oil | 1.03 | 1.26 | 2.28 | 0.81 |
| Ash | 17.50 | 17.03 | 14.36 | 18.46 |
| Undetermined | 8.68 | 12.88 | 13.10 | 15.20 |
Among the undetermined matters are included those of a gummy or resinous composition not extracted by ether, the exact nature of which is not well understood, and the starches, sugars, pentosans and galactan.
Tobacco grown in more northern latitudes has less nicotin than the samples given in the foregoing table.
The following table shows the composition of tobacco grown in Connecticut:[618]
- (A) = Unfermented,
- (B) = Fermented,
| Upper leaves. | Short seconds. | First wrappers. | ||||
|---|---|---|---|---|---|---|
| (A) % | (B) % | (A) % | (B) % | (A) % | (B) % | |
| Water | 23.50 | 23.40 | 27.40 | 21.10 | 27.50 | 24.90 |
| Pure ash | 14.89 | 15.27 | 22.85 | 25.25 | 15.84 | 16.22 |
| Nicotin | 2.50 | 1.79 | 0.77 | 0.50 | 1.26 | 1.44 |
| Nitric acid | 1.89 | 1.97 | 2.39 | 2.82 | 2.59 | 2.35 |
| Ammonia | 0.67 | 0.71 | 0.16 | 0.16 | 0.33 | 0.47 |
| Proteids | 12.19 | 13.31 | 6.69 | 6.81 | 11.31 | 11.62 |
| Fiber | 7.90 | 8.78 | 7.89 | 8.95 | 9.92 | 10.42 |
| Starch | 3.20 | 3.36 | 2.62 | 3.01 | 2.89 | 3.08 |
| Oil and fat | 3.87 | 3.42 | 2.95 | 3.04 | 2.84 | 2.92 |
| Undeterm’d | 29.39 | 27.99 | 26.28 | 28.36 | 25.52 | 26.88 |
600. Estimation of Water.—In the estimation of water in vegetable substances, as has already been noted, it is usual to dry them in the air or partial vacuum, or in an inert gas, at a temperature of 100° until a constant weight is reached. By this process, not only the water, but all substances volatile at the temperature and in the conditions mentioned are expelled. The quantity of these volatile substances in vegetable matter, as a rule, is insignificant and hence the total loss may be estimated as water. In the case of tobacco a far different condition is presented, inasmuch as the nicotin, which sometimes amounts to five per cent of the weight of the sample, is also volatile under the conditions mentioned. It is advisable, therefore, to dry the sample of tobacco at a temperature not above fifty degrees and in a vacuum as complete as possible. Tobacco is also extremely rich in its content of crystallized mineral salts, containing often water of crystallization, and there is danger of this crystal water being lost when the sample is dried at 100°. The desiccation is conveniently made in the apparatus described on [page 22]. If a high vacuum be employed, viz., about twenty-five inches of mercury, it is better not to allow the temperature to go above 40° or 45°. A rather rapid current of dry air should be allowed to pass through the apparatus for the more speedy removal of the moisture and a dish containing sulfuric acid may also be placed inside of the drying apparatus. It is possible by proceeding in this way to secure constant weight in the sample after a few hours.