Native Oil of Laurel —This extraordinary and valuable production is sup posed to be the only known instance of a perfectly volatile liquid obtainable without the aid of art. It is yielded by a tree of considerable height, which is found in the vast forests that cover the flat and fertile regions between the Oronooko and the Parime, in South America. The wood of this tree is aromatic, compact in its texture, and of a brownish colour, and its roots abound with essential oil. The oil is procured by striking with an axe the proper vessels in the internal layers of the bark ; while a calabash is held to receive the fluid which gushes out in such abundance, that several quarts may be caught from a single incision, if the operation be performed with dexterity. In many respects the native oil resembles the essential obtained by expression, distillation, and other artificial processes : it is, however, more volatile and highly rectified than any of them, its specific gravity hardly exceeding that of alcohol. When pure it is colourless and transparent ; its taste is warm and pungent ; its odour aromatic, and closely allied to that of the oily and resinous juice of the conifers. It is volatile, and evaporates without residuum at the ordinary atmospheric temperature. It is inflammable, and, except when mixed with alcohol, gives out in its combustion a dense smoke. Neither the acids nor the alkalies seem to exert any sensible action upon the native oil; when combined, however, with sulphuric acid, the mixture assumes a momentary brownish tinge, but soon regains its transparency. The oil of laurel dissolves camphor, caoutchouc, wax, and resins, and readily combines with volatile and fixed oils: It is insoluble in water; • soluble in alcohol and ether, though the specific gravity of the oil exceeds that of ether ; the compound formed by combining them in the proportion of part of the former to two of the latter floats upon the surface of pure ether; and may, therefore, be the lightest of all known fluids. To the chemist, and the vegetable physiologist in particular, native oil of laurel, elaborated by the unassisted hand of nature, in a state of purity which the operose processes of art may equal, but cannot surpass, presents an interesting subject of inquiry, and a wide field of speculation.
The Oil of Birch Bark, which is so much used in Russia for currying leather, to which it gives a peculiar odour, and a power of resisting moisture beyond any other dressing, is prepared in the following manner :—A large earthen pot is filled with the thin white paper-like external bark of the birch tree, carefully separated from the coarse bark; the mouth of this pot is closed with a wooden bung perforated with several holes. The pot thus prepared is then turned with the mouth downwards, and luted with clay to the mouth of another pot of the same size, which is buried in the ground. The upper pot is now surrounded with fuel, and a fire is made and continued for several hours, according to the size of the pot. When the operation is completed, and the apparatus cooled and unlut4 the lower pot is found to contain a quantity of liquid equal to about 60 per cent. by weight of the bark employed; the liquid consisting of a brown oil mixed with pyroligneous tar, swimming in an acid liquor. In some places iron pots have been substituted for the earthen pots, the mouths being separated by an iron plate pierced with holes. The peculiar odour of the oil is supposed to be owing to a resinous matter which is melted out of the bark, and drops into the lower pot during the process of distillation. In conducting this operation on the large scale, a number of these double pots may be placed in the horizontal bed of a reverberatory furnace, with the lower pots imbedded up to their necks in sand ; by which arrangement a great economy of fuel and labour will be attained.
For fluffier information on the nature and applications of oil, see the articles SPERMACETI, TALLOW, WAX, CANDLES, FAT, SOAP, ELAINE, STEARIN, INS, ESSENTIAL OILS, &C.