Oil of Bergamot spreads instantly; in thirty seconds tiny openings appear, not very abundant, and increase in size slowly; in five minutes they are not larger than oil of nutmeg at one and a half minute. At first they have a dotted border, but as they increase in size this changes to a scalloped film, which spreads, until, in eight or ten minutes, they are joined together over the whole surface. This, with the turpentine oil, gives a watered surface in spreading, much more marked, and with a fine play of colours.
Uses, &c. The volatile oils are chiefly used by perfumers and rectifiers, and in medicine. Some of the cheaper kinds are largely employed as vehicles for colours, and in the manufacture of varnishes. The dose of the aromatic and carminative oils is from 1 to 10 drops, on sugar, or dissolved in a little weak spirit. This does not apply to oil of bitter almonds, the dose of which is 1⁄4 to 1⁄2 a drop.
⁂ The following list includes short notices of nearly all the volatile oils which have been examined, as well as of some other substances of a similar character, which commonly pass under the name.
Oil of Allia′ria. From the roots of Alliaria officinalis, or sauce-alone. Identical with the oil of black mustard.
Oil of All′spice. See Oil of Pimento.
Oil of Al′monds. See Oil of Bitter almonds.
Oil of American Arbor Vitæ. Syn. Huile cedre blanc, Fr. From the fresh tops of Thuja occidentalis, or American arbor-vitæ tree. Yellow; fragrant; stimulant. Used in frictions for rheumatism. Prod. 11⁄2 to 2% (nearly).
Oil of Angel′ica. From the dried root of Angelica Archangelica. Prod. 25% (fully).
Oil of An′iseed. Syn. Oleum anisi (Ph. L., E., & D.), O. essentiale anisi, L. From the fruit (seeds) of Pimpinella anisum, or anise. Nearly colourless. It is very frequently adulterated with one or other of the cheaper oils, in which case spermaceti or camphor is added to it, to make it ‘candy.’
Prop., &c. When pure it congeals into a solid crystalline mass on being cooled to 50° Fahr., and does not melt again until heated to about 63°. Treated with iodine, it quickly congeals into a solid hard mass, with a perceptible increase of temperature, and the development of orange-coloured and grey fumes. Sulphuric acid, with heat, turns it of a rich purple-red colour, and the compound soon afterwards becomes inspissated and hard