In Great Britain the legal provisions exist that finished tobacco must contain not more than 32% of moisture, and that no other substance shall be found therein except essential oils for flavour ing, and olive oil to the extent of 4%, which may be used only in spinning and making up roll tobacco.
The thick portion of the stalk is as a rule removed before the leaf is cut, except in the case of "bird's eye," to which the sec tions of cut stalk give its characteristic appearance. The stripped leaves are then pressed into cakes, more or less lightly when in tended for shag and similar types, and by means of hydraulic presses when flakes are required. The tobacco is then cut into shreds by machine knives operating with a rapid vertical move ment, the speed determining the thickness of the flakes produced. Shags and similar tobaccos are "panned" or roasted, partly to reduce the moisture, and partly to bring out their flavour.
Roll tobacco consists of a filler of broken tobacco which is twisted into a rope and enclosed in a leaf wrapper by means of a spinning wheel. The "brown twist" so produced may be used for chewing purposes, but is usually converted into black or "Irish" roll by coiling the twist into rolls of cylindrical shape, which, after being enclosed in canvas and tightly bound round with rope, are stoved in steam-heated hydraulic presses, and when sufficiently darkened in colour, removed to cold presses to mature.
In cake tobacco the leaves are moulded into shape by pressure, steam presses being used when dark coloured varieties are re quired. Sweetening materials such as glycerin, licorice and sugar are often added to this class of tobacco, although in Great Britain this practice is restricted to bonded factories.
to containing the volatile alkaloid, nicotine, the characteristic con stituent of tobacco, sugar and starch are present in considerable quantities in the bright varieties of leaf, and also salts of such organic acids as acetic, citric, malic and oxalic. In consequence a much higher proportion (about 50%) of the constituents of the leaf is soluble in water than is the case with other plants. The insoluble constituents are made up chiefly of cellulose and pectic acid, which in combination with lime, impart rigidity to the vege table structure, and of albuminous matter and tannin derivatives.
Leaf tobacco is not usually dried below a moisture content of from 12 to 16%, as too dry a condition causes friability. The amount of nicotine ranges from 2% in bright leaf to 5% or more in dark varieties. The proportion of ash obtained from dry tobacco varies from about io% in light leaf to 25% in cigar and other dark varieties.
United States.—Tobacco was first cultivated on a commercial scale in Virginia early in the r 7th century. It is now grown com mercially in eighteen States, the estimated produce for the year 1926 amounting to 1,323,388,00o lb. and valued at $248,752,000. The produce of the chief tobacco-producing States expressed in millions of pounds, was as follows, viz., North Carolina (393), Kentucky (374i), Virginia (I324), Tennessee (107), South Caro lina (574), Pennsylvania (431), Georgia (40), Ohio (38), Wis consin (331), Connecticut (291), and Maryland (29).
Brazil.—The climate and soil are very suitable for cigar leaf and production is steadily increasing. The crop in 1925 amounted to 139,000,000 lb.
Japan.—The Government monopoly controls the growth of tobacco, and the produce is mostly retained for home use. The crop in 1925 exceeded 132,000,000 pounds.