Poley oil (oleum menthæ pulegii).—In Southern France and Spain this oil is obtained by distillation from the leaves of Mentha pulegium. It has an odor resembling that of peppermint, is at first colorless, but soon becomes yellow, has a specific gravity of 0.927, boils at 361.4° to 370.4° F., and contains neither menthol nor carvol. It is used for perfuming herb soaps.
Pimento oil, or oil of allspice (oleum pimenta) from the bruised fruit of Eugenia pimenta, allspice, natural order Myrtaceæ. The oil is pale yellow, becoming reddish-brown by age; it has a very pungent taste and intense odor, very much resembling that of cloves. It is heavier than water, its specific gravity being from 1.021 to 1.037. It mixes with glacial acetic acid in all proportions. When treated with nitric acid, pure pimento oil assumes a red color, with strong effervescence.
Rose oil or attar of roses (oleum rosæ) comes almost exclusively from Bulgaria, where it is obtained by distillation with water from the flowers of Rosa damascena. The small quantities of an excellent quality of rose oil prepared in Southern France from Rosa provincialis remain in the country of their production and do not even cover the local demand. The small productions of Persia and India need also not be taken into consideration. In Tunis, where formerly much rose water was prepared from Rosa canina and also rose oil of a very fine quality, the distillation of roses has, according to Christo Christoff, been entirely abandoned, geranium oil only being now produced. In the summer of 1884, Schimmel & Co., of Leipzic, Germany, made the experiment to obtain oil on a large scale from indigenous roses. The result was very satisfactory, 2000 lbs. of rose leaves yielding about 1 lb. of oil, the extraordinarily agreeable odor of which was so superior to that of the Turkish oil, that notwithstanding the high price—double that of Turkish oil—it found ready purchasers. At the ordinary temperature the Leipzic oil is solid, it only melting at 89.6° F.
In Bulgaria, Kazanlik, in the Tundscha Valley, is the centre of the entire industry and the principal market. Rose oil is there called "gul-jag" (gul, the rose, and jag, oil). The annual production of Kazanlik and neighboring places, amounting 50 years ago to from 450 to 650 lbs., has within a few years risen to the enormous figure of 5500 lbs.
In Kazanlik two varieties of roses, known as the "white rose" and "red rose," are cultivated; the former being Rosa alba, L., and the latter Rosa damascena, Miller. By distillation the white rose yields an oil of little perfume, but rich in stearoptene. On account of its slight odor, the white rose is seldom distilled by itself, but occasionally white and red roses are mixed in order to obtain an oil rich in stearoptene, so that a fraudulent admixture of a larger quantity of geranium oil may be effected without great danger of detection. The large plantations consist only of bushes of red roses. But on the edges of the field a strip, a few feet wide, is planted with white roses, so that only flowers of little commercial value may be plucked by passers-by.
The flowers are gathered before sunrise, and, if possible, the same day subjected to distillation. The latter is effected in a very crude apparatus, over a direct fire. The flowers are distilled with double their weight of water, one-half of which is drawn off. The product of several operations thus obtained is combined and again distilled, when, however, only one-sixth is drawn off. This distillate is allowed to stand for one or two days in a place warmer than 59° F., when the oil floating on the top is skimmed off. It may be supposed that on an average 6600 lbs. of roses are required to obtain 2.2 lbs. of oil, and that these 6600 lbs. of roses correspond to an area of 1 hectare (2.471 acres) planted with rose bushes.
Pure, carefully-distilled rose oil is at first colorless, but soon turns yellowish.[8] Its specific gravity is between 0.830 and 0.890. It consists of a liquid oil and a stearoptene, the content of the latter varying very much. It is a pure hydrocarbon, odorless, of specific gravity, 0.840 to 0.860, and distils at 572° F. Hence it is lighter than the elæoptene on which alone the odor of the rose oil is dependent. Rose oil generally congeals between 50° and 60° F., though sometimes at a higher or lower degree, according to its content of stearoptene. While some oils require the cold of winter for congealing, others are in the heat of summer either entirely solid, or form a fluid filled with many crystals. The odor of rose oil is peculiarly honey-like, and too intense to be agreeable, its entire deliciousness being only developed by strong dilution, be it by dissolving in water or alcohol, or by distribution upon large quantities of rigid bodies, fats, soaps, etc. In alcohol it dissolves with greater difficulty than all other volatile oils, 1 part of it requiring for solution 140 to 160 parts of alcohol of 0.815 specific gravity.
The larger or smaller content of stearoptene in rose oil seems to be dependent on climatic conditions, it having been remarked that the quantity is the greater the lower the temperature of the region. The oil from the coldest and highest regions of the Balkan is richer in stearoptene than that from the lower and warmer regions.
The genuineness of rose oil is generally judged by its odor, its capacity of congealing, and the manner of its crystallization. The odor is by all means the most reliable criterion, but requires much experience, and especially reliable pure standard samples for comparison. The capacity of congealing at certain conditions of temperature, is, to be sure, also a requirement of genuine rose oil, but, as previously mentioned, this property varies very much, and is subject to different influences, so that a fixed standard at which pure rose oil must congeal cannot be established. Attention must, however, be called to the fact that the quality of a rose oil does by no means rise with its greater capacity to congeal, since only the liquid oxygenated portion possesses odor.
Schimmel & Co. bring at present into commerce a liquid rose oil freed from stearoptene which can be highly recommended for finer alcoholic perfumes. It remains fluid at 32° F., but in a cold mixture congeals to a gelatinous mass, and hence is not absolutely free from stearoptene. It has an extremely fine and powerful odor, and when dissolved in alcohol does not give the disagreeable crystalline separations of the ordinary rose oil, which produce a disturbing effect, especially in the preparation of extracts.