oil or essence of bergamot is prooured from the fruit-rind of Citrus Bergamia, a member of the orange family (see Fruit, p. 1025). The tree is cultivated at Reggio, in Calabria, and in Algeria, and is unknown in a wild state ; it oocupies low ground, near the sea. The soil is well irrigated, and cropped with vegetables, and lemon- and orange-trees are often inter spersed among the bergamot-trees. The smooth, thin peel abounds in a peculiarly fragrant essential oil, which is obtained from the full-grown but immature (green) fruits, gathered in November-December. The oil was formerly extracted by distillation, or by expressing the rasped rind ; but these processes have been superseded by the ecuelle, a special instrument described in a separate section (see p. 1457). By this, about 7000 fruits can be treated in a day, the yield of oil being 4-3 oz. from 100 fruits. It is much greener than that extracted by the older processes. During some weeks after extraotion, it gradually deposits much greasy matter, termed " bergs ptene," or "bergamot-camphor," which, after exhaustion by pressure, is distilled with water to recover the final portions of oil it contains. The fruits which have yielded their oil are subjected to expression, and the juioe is concentrated and sold for making citric acid (see Acids, p. 48), while the ultimate residue is consumed by cattle. The oil is thin, mobile, of very fragrant odour bitterish flavour, slightly acid reaction, pale greenish-yellow colour (due to chlorophyll), and sp. gr. ; its boiling-point ranges between 183° and 195° (364°-383° F.) ; it dissolves clearly part of carbon bisulphide, aud is inappreciably soluble in that body. It is never free from adulteration, either with oil distilled from the leaves or residual fruits, or with lemon-oil, or turpentine-oil, or even petroleum. It is shipped principally from Messina and Palermo, in bottles similar to those containing lemon-oil. It is extensively employed in perfumery.
essential oil is extracted from the bark of the common birch (Betala alba), and another from its leaves. The tree or shrub inhabits high N. latitudes in Europe and Asia, being more common than any other tree throughout the Russian empire, and fouud in every wood and grove from the Baltic to the Eastern Ocean. It is numerous in Scandinavia, less so in Scotland, Iceland, and Greenland, and forms little woods at 6000 ft. in Italy. The extraction of birch-bark oil is an industry of some importance in N. Europe and Siberia, and is conducted in the following manner :—An iron pot is filled up with bark, and covered with a close-fitting lid, through which is inserted an iron pipe. On this, is inverted a similar pot, and the rims are carefully fitted together, and well luted with clay. The two are then turned upside down, so that the pot with the bark in it is uppermost. The apparatus is half sunken in the ground, well banked up with a mixture of sand and clay, and a wood fire is kindled round it. When the distillation has continued long enough, the luting is removed, and the pats are separated, when the lower one is found to contain a thin oil floating on pyroligneous acid, or, when the bark has been very impure, on pitch. The yield of pure birch-bark-oil is about one-third by weight of the white bark used. To obtain a centner (120 lb.) of oil, 10-14 trees of 30-50 years old have to be stripped. Now that the value of
standing trees is becoming better understood in Russia, the trees are not felled, as was formerly the custom, but, in many districts, are stripped standing, and left to grow on. In such cases, the outermost bark alone is removed, and that but partially. The underlayers blacken and die, but new bark is formed beneath them, and the growth of the tree continues. The oil should be kept in well-closed vessels, as it is somewhat volatile. It can be refined by boiling over charcoal, and filtering, when it becomes as limpid as linseed-oil, and can be used for similar purposes.
Recently the preparation of this oil has been carried on in Germany and Austria, where it is known as Birkentheer, Birkenol, Jacktenol, or Doggut. This oil is used almost exclusively in the preparation of Russia-leather (see Leather, p. 1236), to which it communicates a peculiar fragrance. The bark is also a valuable tanning material (see Tannin—Birch-bark).
The essential oil obtained by distilling the leaves of the birch with water is colourless, thin, of pleasant balsamic odour, a mild, sweetish, and afterwards peculiarly balsamic, acrid, and hot flavour ; it becomes turbid at 0° (32° F.), but is not hard or crystalline even at —10° (14° F.); and is soluble in 8 parts of alcohol at sp. gr.
Cajuput-oil.—A medicinal oil of some importance (see Drugs—Cajuput, p. 795) is obtained from the leaves of the kayu-puti or "white-wood tree" (Melaleuca minor [Leucadendron Cajuputi]). It is widely spread and abundant in the Indian Archipelago and Malayan Peninsula, and is also tbund in N. Australia, Queensland, and New South Wales. There are many varieties of it, and that grown in the island of Bouro, eastward of Celebes, is said to yield the best oil. The leaves somewhat resemble those of the common willow. They are plucked by hand, placed in baskets, and carried to sheds, where they are emptied into the stills. These are of the usual Malayan form. The leaves and water to be distilled are contained in a cast-iron circular rice-pan, around the margin of which is placed a roll of cloth, forming a tight joint for the reception of the condenser that fits down upon the pan. This condenser consists of a wooden tub without ends, into the top of which is dropped a conical copper tray, kept supplied with cold water ; the products of evapo ration condense upon the lower surface of the tray, and converging to its apex, fall into a spoon shaped spout, which conveys them through a hole in the side of the tub to a receptacle. About 8000 bottles annually are produced in Bouro, valued at about 1 guilder (1s. 8d.) each. It forms almost the only export of this island. The receipts at Singapore in 1871 were :-3895 gal, from Celebes, 445 from Java, 200 from Manilla, and 350 from other places ; total, 4890 gal. Of this, the greater portion was re-exported to Bombay, Calcutta, and Cochin China. The oil arrives here from Singapore and Batavia in common beer- and wine-bottles. It is a transparent mobile fluid, of light bluish-green colour (due to presence of copper, but rarely if ever in dangerous quantity), fragrant camphoraceous odour, and bitterish aromatic flavour ; its sp. gr. is 0.926; it remains liquid even at — 13° (8/° F.), and boils at 175° (347° F.) ; and dissolves readily in alcohol.