THE VOLATILE OILS USED IN PERFUMERY.

The volatile oils, as previously mentioned, may be divided into three groups, viz: the pure hydrocarbons, oxygenated oils, and sulphuretted oils. Chemically, this division is, however, of little value, since, among bodies which should be classed according to it in one of the groups, combinations are found which vary very much in a chemical respect, and belong partially in the groups of alcohols, indifferent bodies, acids, etc.

It is, therefore, preferred not to attempt a classification of the volatile oils according to their chemical composition, but simply to enumerate them in alphabetical order.

Acacia, oil of, commonly called oil of cassie. The flowers or buds of the acacia Farnesiana yield a somewhat thickly-fluid, greenish-yellow oil of a very intense but delightful odor. The oil may be obtained either by extraction or absorption. The acacia is cultivated in special plantations along the Riviera di Genova. These plantations being controlled by a few perfumers, the oil is not allowed to reach the market, and does not form an article of commerce. The green-colored extrait d'acacia is a solution of the oil in alcohol.

Almond oil (bitter) (oleum amygdalae amaræ) is obtained by submitting bitter almond cake (left after the expression of the fixed oil from bitter almonds) to distillation with water. The volatile oil does not exist ready formed in the bitter almond, nor in the almond cake, but results from the decomposition of a glucoside called "amygdalin," contained in the cake, under the influence of emulsin and water, the emulsin acting as a ferment, into benzylic aldehyde, glucose and prussic acid. The almond tree grows wild, but is also cultivated in Southern Europe, Africa, Barbary, Palestine and Syria. The bitter almonds brought from Barbary are considered the best. Besides, in almonds, amygdalin occurs in various other plants; for instance, in the leaves of the cherry laurel, the leaves and kernels of the peach, the kernels of the black cherry and other varieties of prunus and amygdalus, they all yielding, after maceration with water, a distillate containing prussic acid and oil of bitter almonds.

Instead of the comparatively expensive bitter almonds, peach kernels freed from their hard shells are extensively used in the fabrication of oil of bitter almonds. The oil is prepared as follows: The press cakes of bitter almonds or peach kernels are ground and soaked about twenty-four hours in twice their weight of water to which one-third their weight of salt has been added. The whole is then submitted to distillation. The temperature of the water should not exceed 113° to 122° F. The emulsin contained in the almonds possesses only within certain limits of temperature the power of decomposing amygdalin, and, if heated to 176° F., becomes inoperative. Hence, if the almond paste is quickly heated to boiling, the emulsin becomes inoperative before all the amygdalin is decomposed, and a portion of it being consequently lost, the yield is insufficient. The distillation of the almond paste is effected in a current of steam.

A portion of the prussic acid formed by the decomposition of the amygdalin adheres tenaciously to the oil. This content of prussic acid makes the oil of bitter almonds exceedingly poisonous, while in itself it is non-poisonous. It can be freed from the prussic acid by shaking with ferrous sulphate (blue vitriol) solution. By then distilling over burnt lime the originally yellow or yellowish oil is obtained colorless. It is then thinly fluid, of a peculiar agreeable odor and strongly nutty taste. Its specific gravity is 1.043 at 59° F., but varies a little with age. It boils at 356° F., and dissolves in 13 parts of water, but more readily in alcohol and ether. In the air it is rapidly converted into benzoic acid by the absorption of oxygen. It has to be carefully protected from air and light and kept in well-closed bottles in a dark place. The crude oil, containing from 2 to 5 per cent. prussic acid, has generally a yellowish color.

Oil of bitter almonds may be prepared artificially in many ways. By allowing chlorine to flow into boiling toluene, the latter is converted into benzyl chloride:-

By withdrawing the chlorine and one atom hydrogen from the benzyl chloride and introducing for it one atom oxygen, the benzyl chloride is converted into benzaldehyde. This conversion is readily effected by continuously boiling, best with the introduction of carbonic acid, 1 part of benzyl chloride with 1½ parts of lead nitrate and 10 parts of water, and finally distilling the benzaldehyde off by steam. The decomposition takes place according to the following equation:—

2[C₆H₅(CH₂Cl)] + Pb(NO₃)2 =
2[C₆H₅(CHO)] + PbCl₂ + N₂O₃ + H₂O.

The crude benzaldehyde thus obtained is agitated with warm solution of acid sodium sulphite, the solution formed thereby is separated from undissolved oily particles and cooled, whereby a combination of benzaldehyde with acid sodium sulphate crystallizes out. This combination is separated from the remaining fluid, decomposed by acid and submitted to distillation, whereby benzaldehyde passes over. Large quantities of benzaldehyde are at present prepared according to this method. The identity of benzaldehyde with oil of bitter almonds has been established by Lippmann and Hawliczek.

Genuine oil of almonds is much adulterated, chiefly with alcohol, nitrobenzole, and various cheaper oils. An addition of 3 to 5 per cent. of alcohol is frequently made by Italian dealers in order to conceal a content of water, which at a low temperature is apt to render the oil turbid. To detect the presence of alcohol, moderately heat a sample of the oil in a distilling apparatus and compound the drops, first passing over with sodium carbonate solution and then with potassium iodide solution. In the presence of alcohol a yellowish crystalline precipitate of iodoform is formed.

An addition of synthetically composed oil might seem of no importance, since the natural oil does not differ from it. However, for very fine perfumery the natural oil cannot be replaced by the artificial, it having been thus far impossible to obtain the latter absolutely chemically pure. It always contains small quantities of undecomposed chlorine combinations which injure the taste and odor. To detect such oil in the natural oil, bring a few drops upon a tuft of cotton and ignite it. Over the burning flame invert a beaker moistened inside with water. On the moist sides of the beaker the soot and hydrochloric acid formed by the combustion of the chlorine combination are precipitated. When the flame is extinguished, the beaker is rinsed out with water, the fluid filtered and tested for chlorine with nitrate of silver. An addition of 10 per cent. artificial oil can in this manner be accurately determined.

If genuine oil of bitter almonds containing prussic acid, be heated with an excess of alcoholic potash lye, and the excess of the latter be neutralized with hydrochloric acid, benzoin amounting to 40 to 50 per cent. of the weight of oil of bitter almonds is, according to A. Kremel, separated. By subjecting artificial oil of bitter almonds to the same treatment, no benzoin is separated, so that the genuine oil can in this manner be distinguished from the artificial. Kremel further found that oil of bitter almonds prepared from apricot kernels, when treated in an analogous manner, yielded considerably less benzoin, and that cherry-laurel oil containing prussic acid, which has been considered identical with oil of bitter almonds, separated no benzoin whatever. Should further experiments prove the constancy of this phenomenon, this reaction would be a convenient means of distinguishing the four products.

An adulteration with nitrobenzole and other volatile oils is recognized by mixing 2 drops of the oil with 100 drops of distilled water, and shaking vigorously. Pure oil must completely dissolve. However, the test yields accurate results only with the use of actually pure distilled water and by accurately observing the above-mentioned proportions. If to 5 cubic centimeters of 90 per cent. alcohol and an equal quantity of distilled water in a test-tube, 10 drops of the oil be added, and, after closing the tube with the finger, mixture be effected by gently turning the tube twice upside down, a clear solution will immediately result if the oil is pure. If, however, it contains nitrobenzole, even only 1 per cent., the latter separates, at first rendering the fluid turbid, but in the course of a minute, when gently agitated, it floats in the form of minute drops upon the fluid, while, when at rest, these drops collect to larger ones on the bottom of the test-tube. If the oil becomes only turbid, adulteration with other volatile oils is indicated. Another test, given by Wagner, is based upon the difference in the specific gravity of mixtures of oil of bitter almonds with oil of mirbane. The specific gravity of commercial oil of bitter almonds varies between 1.040 and 1.043 and that of oil of mirbane between 1.180 and 1.201.

5 c. c. of pure oil of bitter almonds weigh 5.29 grammes.
5   "   mixed with ¼ oil of mirbane     "     5.39     "
5   "       "       "    ½   "           "            "     5.57     "
5   "       "       "    ¾   "           "            "     5.75     "
5   "   of pure           "             "           "      5.90     "

Oil of bitter almonds is much used in the fabrication of perfumery. In a pure state its odor is by no means agreeable, but rather strong and stupefying. When strongly diluted it is, however, very pleasant.

Angelica oil is obtained by distillation with water from the root of Angelica Archangelica L., natural order Umbelliferae. The oil is lighter than water, possesses the spicy odor of the root and an aromatic pungent taste. It consists mostly of a terpene which turns the plane of polarization to the right, and boils at 320° F.

Besides the oil from the root, one obtained from the seeds also occurs in commerce. It is, however, more expensive. In a fresh state it is amber-yellow, and has a specific gravity of 0.8549 at 59° F.; older oil is thickly-fluid, brown, and has a specific gravity of O.9086. It contains a terpene which turns the plane of polarization to the right, and has a lemon-like odor. It is used for fine perfumery.

Anise-seed oil (oleum anisi). The anise (Pimpinella anisum L.), natural order Umbelliferae, contains volatile oil in all parts, but chiefly in the seeds. Dry anise-seed yields by distillation 2½ to 3 per cent. of oil, while the peduncle and chaff contain at the utmost 1 per cent. of oil, which is said to be richer in stearoptene. The anise-seed oil prepared in Southern Russia has always been highly valued, but as it is generally considerably adulterated, the Leipsic manufacturers of volatile oils prefer to import the seed and distill it themselves.

Freshly prepared anise-seed oil is colorless or straw-yellow, has the odor of anise and a sweetish taste, leaving a burning sensation upon the tongue. It is thinly fluid at 68° F., but commences to congeal at a somewhat lower temperature, and the sooner the more stearoptene it contains. Good oil should become solid at from 57.2° to 60.8° F. It has a specific gravity of 0.980 to 0.995 at 59° F. The specific gravity varies with the content of stearoptene; the greater the latter the higher the specific gravity. Good anise-seed oil contains 5 to 10 per cent. of terpene and 90 to 95 per cent. of a stearoptene, called anethol, C₁₀H₁₂O, on which the value of the oil depends. The anethol can be separated from the oil by cooling to 32° F., and forms colorless crystals. It has an agreeable odor and intensely sweet taste, is sparingly soluble in water, but readily in alcohol, ether, and other solvents of volatile oils. Good anethol has a specific gravity of 0.986, and melts at 69° to 70° F. By frequent contact with the air a small portion of the anethol is oxidized, very likely to anisaldehyde. By this process the specific gravity is raised and the melting point lowered.

Anise-seed oil is soluble in 5 parts of 90 per cent. alcohol, and with 3½ times its volume of petroleum-ether yields a clear mixture. Its mixture with four times its weight of petroleum-ether is turbid, but becomes clear in ten minutes, while that with five times its volume of petroleum-ether remains for a longer time turbid. In a fluid state the oil, when exposed to the air, becomes resinous and loses its property to crystallize. It should, therefore, be kept in tightly-closed bottles in a cool, shady place.

Anise-seed oil is used in perfuming soaps and mouth waters. It should, however, be used with prudence, since the sweetish, penetrating odor of the oil readily overcomes the other volatile oils in the mixture, and renders them inoperative.

Star anise oil very much resembles the ordinary anise-seed oil. It is obtained from star anise, the fruit of Illicium anisatum, a tree formerly supposed to be indigenous to Cochin China, and cultivated in China, Japan, and the Phillipine Islands. However, according to Messrs. Bourgeoin-Meiffre, a French firm of Hanoï (Tonkin), the star anise oil found in commerce is exclusively produced in the French colony Tonkin (Province Langson), the French government having made over the entire sale of the oil to the above-mentioned firm.

According to a memoir published by Dr. Blondel, of Paris, the star anise tree is not indigenous to the Chinese provinces Yunnan, Quang-si, and Fo-Rien, but to the province Langson, which has by conquest passed into French possession. Hence, the producers of star anise and star anise oil are now under French control and, as it seems, are obliged to sell all the oil produced to the above-mentioned firm. If these statements should prove correct, the Chinese harbors Macao and Hong Kong, from which the greater portion of star anise oil was formerly exported, will lose their importance in this respect and the product find its way direct from Hanoï via Hayphong to Marseilles. The first shipment from Bourgeoin-Meiffre arrived in Europe in December, 1890. According to Messrs. Schimmel & Co.'s report, the product is put up and packed exactly like that formerly shipped from Hong Kong, and the oil of excellent quality.

Star anise oil differs from the ordinary oil in containing a much smaller quantity of anethol, and hence congealing only at a temperature of from 41° to 50° F. Besides the odor of the terpene contained in star anise oil differs from that of the ordinary oil. Admixtures of star anise oil can, therefore, be generally recognized by the odor. Other methods recommended for its detection are unreliable.

Balm oil.—The leaves of this plant, Melissa officinalis, yield by distillation a volatile oil sometimes called oil of melissa. It is colorless or yellowish, of a pleasant odor, has a specific gravity of 0.85 to 0.92, shows a slightly acid reaction and dissolves in 2 to 3 parts of alcohol. It must not be confounded with the so-called East India oil of melissa or citronella oil from Andropogon Nardus L. Balm oil is occasionally used in the preparation of eau de Cologne.

Basil oil is distilled in Southern France from the fresh leaves of Ocymum basilicum L., natural order Labiatæ. The oil shows the peculiar odor of the herb and crystallizes a few degrees above 32° F. In perfumery it is used as an addition to violet and other preparations. The French also prepare a pommade basilique, which serves as a cheap substitute for violet pomade.

Bayberry oil, or oil of bay leaves, is extracted by distillation from the leaves of Myrcia acris or the bayberry tree. Many varieties of the tree exist throughout the West Indies, which are scarcely to be distinguished botanically, but have quite a different odor from that of the genuine tree. Great care must, therefore, be taken in the collection of the leaves which are to be used, as the admixture of a small quantity of the other leaves may entirely spoil the product of distillation. Two oils are obtained, a light oil of specific gravity of 0.870 to 0.990, and a heavy oil with specific gravity 1.023 to 1.037. When first distilled the oil is colorless, but by exposure to the air quickly acquires a yellowish tint and, if the exposure be continued, becomes quite dark in color. The odor of the freshly-distilled oil is rank, but in the course of from three to six months it becomes mellow, and ripens into the agreeable fragrance so much liked in the best specimens of bay-rum. The oil is soluble in all proportions in 95 per cent. alcohol, also in ether and petroleum benzine. Its chief use is for the preparation of bay-rum.

Bergamot oil is obtained from the rinds of the fruit of citrus bergamia, a tree belonging to the natural order Aurantiaceæ. The rind is grated and the oil running off separated from the aqueous fluid and cellular substance by means of a separating funnel, or the grated mass is distilled in a current of carbonic acid. The oil is very fluid and pale yellow, but poorer qualities are frequently greenish or brownish. When distilled with water it becomes perfectly colorless, but is less durable. Its odor is very pleasant, somewhat like a mixture of orange and lemon oils. Its specific gravity is 0.87 to 0.89. By standing for some time, the oil separates white crystalline scales (stearoptene), which melt at 223° F. The oil becomes solid a few degrees below the freezing point. The Messina oil of bergamot is considered the best. From other volatile oils of the orange family, bergamot oil differs in dissolving readily in caustic potash, forming a clear solution. It has, however, the same property as other oils of a similar origin, of igniting with iodine and not dissolving santalin, the red resinous coloring matter of santal-wood.

Bergamot oil may be tested as to its purity by mixing it with alcohol. It becomes pale gray-yellow, forms a sediment which adheres firmly to the vessel and, on shaking, floats about in the form of flakes. After two days the sediment is inconsiderable and difficult to divide into flakes in the clear yellow fluid by shaking. The oil is frequently adulterated with alcohol. To detect such adulteration, Righini recommends the following method: Mix 15 parts of the oil with a like quantity of pure olive oil or oil of sweet almonds. If alcohol is present, it immediately separates, like water, from the fat oil; if no separation takes place the oil is not adulterated with alcohol. The tannin test also gives reliable results. In storing oil of bergamot great care must be exercised to exclude air and light, as it is one of the most changeable oils and soon acquires an odor resembling that of turpentine.

Large quantities of oil of bergamot are used in perfumery. It forms, so to say, the basis for most of the finer products. In Cologne water it forms the principal constituent in the mixture of volatile oils.

Cajeput oil (oleum cajeputi).—This oil is obtained by distillation from the leaves of several species of Melaleucæ, natural order Caryophyllaceæ, indigenous to the East Indies, Banda, and Malabar. The ordinary oil has a greenish color and possesses a strong odor of camphor and a pungent taste. It is chiefly imported by way of Amsterdam, where it is partially discolored by rectification, so that two kinds, the white and green cajeput oil, are brought into commerce. The color of the latter is generally supposed to be due to a resinous substance containing chlorophyl, though others assert that it originates from the copper of the distilling apparatus and the copper flasks in which it is dispatched. The specific gravity of the oil varies between 0.910 and 0.940, though specifically lighter and heavier oils are said to occur.

It is claimed that an artificial cajeput oil is often prepared from camphor and rosemary oil, the green color being obtained by distillation with milfoil. The presence of camphor may be readily determined by thoroughly triturating a few drops of the oil with sugar and then dissolving in water, whereby the particles of camphor separate in the form of white flakes upon the surface.

Cajeput oil is frequently adulterated with oil of turpentine and rosemary oil. Such adulteration is recognized by pure cajeput oil dissolving clear in equal parts of 90 per cent. alcohol, which is not the case with the other two oils.

Camomile or chamomile oil (oleum anthemidis).—Two varieties of oil of camomile are found in commerce, one green and the other blue. The first is derived from the flowers of the genuine or Roman camomile (Anthemis nobilis) and the blue from the common variety (Matricaria chamomila). The last oil is the one chiefly used in the manufacture of perfumery and in medicine.

Blue camomile oil is generally obtained by distillation. In distilling, metal Florentine flasks should be used, as the oil adheres tenaciously to glass vessels and the distillate has to be treated with ether. The pure oil has a beautiful blue color, and on heating forms blue vapors. It has a penetrating odor which only by strong dilution becomes similar to that of camomile. By storing in the light and the simultaneous presence of air, the oil turns green; later on, brown, and is finally converted into a thickly-fluid, brownish mass.

Green camomile oil from the genuine or Roman camomile possesses an agreeable odor of fresh lemons; it is more seldom used than the other.

On account of the slight yield obtained from the flowers, camomile oil is rather expensive.

Caraway oil (oleum carui) is obtained by distillation from the seeds of the well-known aromatic plant Carum carui, or the caraway, natural order Umbelliferæ. In a fresh, purified state the oil is colorless, very thinly-fluid and possesses a pungent taste. The oil prepared from cleansed Dutch seed is best liked, while that distilled from Norwegian or Tyrolese seed is not much in demand, its taste and odor not being so pure on account of the many impurities mixed with these kinds of seed.

Caraway oil consists mainly of a terpene, C₁₀H₁₆, called carvene, specific gravity 0.870, and of carvol, specific gravity 0.960. The richer the oil in carvol, the higher its specific gravity. Good caraway oil should have a specific gravity of 0.900 to 0.910. The carvol being the actual bearer of the aroma, the value of the oil exclusively depends on the content of it. In the better varieties of oil, the content of carvol amounts to from 45 to 50 per cent., while poorer qualities generally contain only from 40 to 42 per cent. The carvol and carvene are now frequently separated by fractional distillation. The carvol, which has three times as strong an odor and taste as the carvene, dissolves with much greater facility in alcohol. The carvene being offered at very low prices might be suitable for perfuming cheap soaps.

Caraway oil obtained by distillation from the plant has a less agreeable odor than that from the seed, and possesses an acrid resinous taste.

The purity of caraway oil is recognized by its dissolving clear in equal parts of 90 per cent. alcohol. If such is not the case, the oil contains either an admixture of oil of turpentine or does not possess the full normal content of carvol. Pure caraway oil does not detonate with iodine, which is the case with oil containing oil of turpentine.

Caraway oil is chiefly used for perfuming soap; for handkerchief perfumes it is not suitable.

Cedar oil (oleum cedri) is obtained by distillation from the shavings of the wood of the American or Virginia cedar (Juniperus virginiana). For the distillation of oil the waste falling off in the manufacture of lead-pencils is almost exclusively used. It yields about 2 to 3 per cent. of oil. The oil is thinly-fluid, of specific gravity 0.9622, of a greenish color, and an agreeable but not very penetrating odor. It is a mixture of a terpene, boiling at about 540° F., and of a hydrocarbon. The latter, which is called cidrin, forms the fluid portion of the oil. It has a specific gravity of 0.984, and boils at about 459° F.

Cedar oil is extensively used in the manufacture of toilet soap, it serving as the basis for other perfumes. Care must, however, be taken that its odor does not preponderate, as in such case it readily produces an unpleasant effect. The oil being cheap, adulteration is scarcely to be feared.

A volatile oil is also obtained by distillation from the leaves of the Juniperus virginiana. In odor it resembles savin oil, and is unfit for perfuming purposes.

Cherry-laurel oil (oleum laurocerasi) is the volatile oil, which contains prussic acid, obtained from the leaves of the cherry-laurel (Prunus laurocerasus, L.). Like bitter almonds, the leaves contain some amygdalin. Hence they are macerated with water and allowed to stand in a warm place for 24 hours. By subsequent distillation a volatile oil is obtained which closely resembles oil of bitter almonds, but differs in some respects. It is colorless or yellowish, rarely reddish, and of specific gravity 1.05 to 1.06. In its behavior towards air, solvents, and reagents, it does not essentially differ from oil of bitter almonds.[5]

To detect oil of mirbane in cherry-laurel oil, Enrico Pega adds some alcohol to the oil to be tested and then mixes it with some alcoholic potash lye and a few drops of ferric chloride solution. After standing for a few hours the mixture is shaken and distilled. A small portion of the oil distilling over is freed from water, poured upon a few small pieces of pure caustic potash in a test-tube, and heated over a lamp. If the sample is pure it remains colorless; in the presence of oil of mirbane it acquires a dark coloration in consequence of the formation of nitrobenzide and aniline, a few drops of calcium chloride solution brought into the mixture producing, for this reason, a violet coloration.

Cherry laurel oil is but seldom used for perfuming purposes.

Cinnamon oils.—There are four different kinds of this oil, viz., Ceylon cinnamon oil, cassia oil, cinnamon root oil, and oil of cinnamon leaves. Though the first two are very much alike, the Ceylon oil is considered the best.

Ceylon cinnamon oil (oleum cinnamoni ceylonici).—Formerly this oil was exclusively distilled from chips and waste of the genuine cinnamon bark of the Cinnamonum ceylonicum, Nees, and came into commerce from Ceylon. However, the fabrication of the oil from cinnamon waste or chips is now extensively carried on in Germany, and this oil, being prepared with the assistance of more perfect apparatus, has almost entirely supplanted that exported from Ceylon.

When fresh, the Ceylon oil is colorless, but when stored for some time it becomes first golden yellow and later on brownish. It is thickly-fluid and heavier than water, its specific gravity being 1.060 to 1.090. It has an agreeable, aromatic odor and a biting but pure, sweet taste. Its principal constituent is cinnamaldehyde (C₉H₈O), and it contains, besides, 4 to 8 per cent. of eugenol. The presence of the latter in cinnamon oil may be established by shaking with 15 per cent. soda-solution, whereby the eugenol is dissolved, and decomposing the aqueous solution with hydrochloric acid. The eugenol separated thereby gives in alcoholic solution, when compounded with a trace of ferric chloride, a beautiful blue color.

Cassia oil (oleum cassiæ).—In China and Cochin China this oil is obtained by distillation from the bark, unripe fruits, buds, and other waste of the Cinnamonum cassia or Cinnamonum aromaticum, Nees, a tree indigenous to those countries. It has a pale yellow color, which in time becomes brown. It is thickly-fluid, of specific gravity 1.05 to 1.07, and possesses a sweet taste with an acrid after-taste. Like cinnamon oil, it consists chiefly of cinnamaldehyde, but contains no eugenol, and hence can be readily distinguished from Ceylon oil by the above-mentioned reaction. One part of pure cassia oil dissolves in two parts of 80 per cent. alcohol.

Cinnamon root oil and oil of cinnamon leaves.—Neither of these oils contains cinnamaldehyde, but abundant quantities of eugenol, the root oil as much as 50 to 70 per cent. The root oil is quite limpid and has an agreeable odor of cinnamon and cloves. The leaf oil is thickly-fluid, of the consistency of castor oil.

The Ceylon oil is frequently adulterated with cassia oil. Such adulteration is very difficult to detect, and can only be recognized by experts by the odor and taste.

The quality of cassia oil is recognized by the taste and odor, especially on heating, and the high specific gravity, in consequence of which the oil sinks in water. According to Hager, cassia oil is frequently adulterated with oil of cloves. This is, however, scarcely probable, the price of oil of cloves being, on an average, higher than that of cassia oil. The latter, however, is frequently adulterated with cheaper thickly-fluid volatile oils, especially with cedar oil. In this case the oil does not dissolve in the above-mentioned proportion in alcohol.

The value of cassia oil is dependent on its contents of cinnamaldehyde. Hence, the establishment of its actual value requires a quantitative determination of its contents of cinnamaldehyde, which unfortunately presents great difficulties. For this purpose Schimmel & Co. proceed indirectly as follows: 75 grammes of cassia oil in a capacious boiling flask are mixed with 300 grammes of a boiling-hot 30 per cent. solution of acid sodium sulphite, whereby cinnamaldehyde-sodium sulphite is immediately separated. The whole is then vigorously agitated and allowed to rest for a short time. (With oils rich in aldehyde considerable heating generally takes place, which must eventually be moderated by the addition of cold water.) Next add about 200 grammes of hot water and heat the whole, with frequent shaking, in the water-bath until the combination of the aldehyde with the acid-sodium sulphite is completely dissolved, and the non-aldehydes in the form of an oily layer float upon the solution of the aldehyde salt. Now allow the whole to cool, then shake twice with ether; first, with about 200 cubic centimeters, and then with 100; combine the ethereal extracts of the non-aldehydes separated by means of a separatory funnel, and filter them into a capacious, previously-weighed beaker provided with a platinum wire, the lower end of which is bent in the form of a spiral. Now evaporate the ether as much as possible, by placing the beaker in hot water. When by swinging the beaker the remaining fluid no longer foams up, allow to cool off and weigh. Now return the beaker-glass to the water-bath for ten minutes, weigh again after cooling, and repeat the operation until the difference between two weighings does not amount to more than 0.3 gramme at the utmost. The weighing previous to the last is taken as the correct one.[6]

The weight of the non-aldehydes thus obtained is deducted from the cassia oil used, the difference giving the content of cinnamaldehyde in the latter.

For example:—

By accurately following the directions given, the difference between two controlling determinations will be only a few tenths per cent., seldom as much as 1 per cent. For practical purposes, for which alone this method is intended, this is more than sufficient.

According to the reports of Schimmel & Co., all the cassia oil brought into commerce from China was for a considerable time adulterated with resin and petroleum, they having found as much as 30 per cent. of resin in the oil. Such adulteration can be established by the determination of the specific gravity and distilling the oil. Good cassia oil should show a specific gravity of 1.05 to 1.07 at 59° F., and by distillation 90 per cent. of pure cassia oil must pass over. The residue should not solidify after cooling and acquire the character of a brittle resin; it must remain at least thickly-fluid, and under no conditions amount to more than 10 per cent.

Citron oil (oleum citri), from the peel of the fruit of Citrus medica or the citron tree. The oil is prepared in a similar manner to that of oil of bergamot, either by expression or distillation, the latter process yielding more and purer oil.

Rectified citron oil is colorless, of an agreeable penetrating odor and acrid taste, and very sensitive to light and air. By exposure to light it turns yellow, and if air be admitted at the same time, it is first converted into a fluid which, on account of its content of ozone, possesses strong bleaching powers. The oil at the same time acquires a disagreeable odor, resembling that of oil of turpentine, and is finally converted into a resinous mass.

Citron oil is frequently adulterated with oil of orange and sometimes with oil of bergamot. These adulterations are readily detected by an experienced person by the odor, this being in fact the best guide. The specific gravity of citron oil is 0.850 at 59° F.; it boils at from 332.6° to 343.4° F. and congeals at 4° F.

Citronella oil (oleum citronellæ) is chiefly distilled in Ceylon from the lemon grass, Andropogon Nardus, L. It is quite limpid, of a greenish-yellow to brown color, and has an odor resembling that of genuine citron oil. Its specific gravity is 0.896 at 59° F., and it boils at from 392° to 410° F. Of the various oils reaching the market that with the trade-mark "Fisher" is most in demand, it being distinguished by special purity. Edward Kremers has found in citronella oil an aldehyde, C₇H₁₄O, a terpene, C₁₀H₁₆, citronellol, which is isomeric with borneol; further, acetic acid and valerianic acid.

The Indian distillers, it is claimed, adulterate the citronella oil with petroleum, an addition up to 25 per cent. being not uncommon.

According to experiments by Schimmel & Co., pure citronella oil must give a clear solution, when 1 part of the oil is vigorously shaken with 10 parts of 80 per cent. alcohol. If, in executing the test, the kind of turbidity is observed, and whether the portion insoluble in alcohol separates, after standing, upon the surface or on the bottom of the fluid, and further, if the above-mentioned quantity of alcohol is not added at one time, but at first only 1 or 2 parts of it, a conclusion may be drawn as to the kind and quantity of the adulterant.

Petroleum causes a milky-white turbidity, while in the presence of fat oil the mixture becomes turbid, but not actually milky. As a rule, fat oil deposits, after standing, on the bottom, while petroleum floats upon the surface of the fluid. Citronella oil adulterated with fat oil does not dissolve in 1 to 2 parts nor in 10 parts of 80 per cent. alcohol, while oil adulterated with not too large a quantity of petroleum, gives a clear solution with 1 to 2 parts. The determination of the specific gravity may also serve for the detection of adulterations. This holds good, however, only for petroleum, which reduces the specific gravity, an addition of fat oil producing no deviation in this respect. The specific gravity of the oil should not be below 0.895 at 59° F.

Citronella oil is much used for perfuming cheap hair oils and toilet soaps; it is the chief constituent of all perfumes for honey-soaps. In the American soap industry it is extensively used, the yearly consumption being estimated at 1½ million ounces.

Cloves, oil of (oleum caryophylli), is obtained by distillation with steam, or by extraction from the cloves of commerce, which are the dried unexpanded flower buds of Caryophyllus aromaticus, L., or the clove tree. Oil of cloves, when fresh, is almost colorless, but on exposure to air acquires a brownish coloration and a thickly fluid consistency. It has the aromatic taste and odor of cloves, and a specific gravity of 1.300 to 1.065. It frequently shows a slightly acid reaction, boils at 482° F., and congeals at 4° F. It is readily soluble in alcohol, ether, and strong acetic acid. It consists of a terpene (C₁₀H₁₆) and eugenol (C₁₀H₁₂O₂), the odor of the oil being due to the latter. The terpene has a specific gravity of 0.918, and in distilling passes over first (light oil of cloves). The eugenol, when fresh, is colorless, has the odor and taste of cloves, a specific gravity of 1.063 at 65° F., boils at 487.4° F., is insoluble in water and glycerin, but soluble in alcohol, ether and glacial acetic acid. Its alcoholic solution is colored magnificently blue by ferric chloride. If in an alkaline solution it is oxidized with potassium permanganate, vanillin being formed.

An inferior quality of oil is obtained from the stems of the clove buds. It dissolves with greater difficulty than the oil prepared from the buds, and has a darker red-brown color.

To test the value of oil of cloves, introduce, according to Stohman, into a graduated glass cylinder 10 volumes ether, 10 oil of cloves, and 30 of a 10-per cent. soda solution. After vigorous shaking, the eugenol dissolves; the increase in volume of the aqueous fluid is then proportional to the quantity of eugenol present. For more exact determinations, dissolve a weighed quantity of oil, repeatedly shake the aqueous fluid with ether to remove the terpene, then decompose the eugenol-sodium with dilute sulphuric acid, dissolve the separated eugenol in ether and weigh after evaporating the ethereal fluid. Good oil of cloves does not contain less than 80 per cent. of eugenol, and frequently 90 per cent. or more.

Oil of cloves is chiefly adulterated with copaiba oil and cedar oil. Such adulteration is recognized by the oil not forming a clear solution in every proportion with alcohol, as is the case with pure oil of cloves.

Oil of cloves is much used for perfuming purposes.

Eucalyptus oil (oleum eucalypti) is obtained from the leaves of various trees of the eucalyptus family. According to Merk two kinds of oil must be strictly kept apart: oleum eucalypti from the leaves of eucalyptus globulus and oleum eucalypti australe, the former being used in medicine, and the latter, which is considerably cheaper, chiefly for perfuming purposes. However, Piesse's opinion that eucalyptus oil, as far as its odor is concerned, does not deserve to be classed among perfumes is undoubtedly correct. It has an odor between that of oil of turpentine and cajeput oil, and as long as perfumery is the art of sweet odors, such oil cannot be designated a perfume.

When not rectified, eucalyptus oil is mostly yellowish or bluish. In a rectified state it is colorless, clear, limpid, lighter than water, of a strong odor, and acrid taste. The oil from eucalyptus globulus has a specific gravity of 0.900 to 0.925, and dissolves in every proportion in 90 per cent. alcohol. It is optically inactive or turns the plane of polarization slightly to the right. On standing with sodium it acquires a yellowish coloration, and does not detonate with iodine. The oil from eucalyptus australe has a specific gravity of 0.86 to 0.87, and is but sparingly soluble in 90 per cent. alcohol, so that even a solution prepared in the proportion of 1:15 is turbid. It turns the plane of polarization strongly to the left; acquires, on standing with sodium, a red coloration, and detonates with iodine.

Eucalyptus oil consists of eucalyptol and eucalyptene, and perhaps other hydrocarbons. The content of the first, on which depends the medicinal value of the oil, varies very much in the oils from the different species of eucalyptus, the oil from some species, it is said, containing no eucalyptol whatever.

Eucalyptol (C₂₄H₂₀O₂) is limpid, colorless, turns the plane of polarization, has a specific gravity of 0.905, and boils at 347° F. Its vapor mixed with air has an agreeable, refreshing taste, and its dilute solutions remind one of roses. Eucalyptene (C₂₄H₁₈) has a specific gravity of 0.836, and boils at 329° F.

Fennel oil (oleum fœniculi) is derived by distillation from the fruits of Fœniculum vulgare, Gaertner. Large quantities of it are produced in Saxony, and also in Galicea. It is quite colorless, limpid, of specific gravity 0.940 to 0.970 and, with a full content of stearoptene, possesses a nauseous sweet taste and odor. It contains 60 to 70 per cent. of anethol and congeals at from 41° to 50° F. to a crystalline mass. The leaves of the plant also contain a volatile oil, which is, however, less valued than the seed-oil.

Good fennel oil should dissolve clear in 1 to 2 parts of 90 per cent. alcohol. Direct adulterations of this oil do not occur, but the stearoptene is frequently withdrawn by fractional distillation whereby the oil loses much in value. Such oil freed from stearoptene does not congeal, has a more bitter than sweet taste and does not dissolve in the above-mentioned proportion in alcohol.

In perfumery fennel oil is but little used; sometimes in connection with other volatile oils for perfuming soaps.

Geranium oil, palmarosa oil, Turkish geranium oil is obtained from Andropogon Pachnodes. It is yellowish, limpid, of specific gravity 0.890 at 59° F., possesses a very agreeable rose-like odor resembling that of geranium oils from Pelargonium radula, Aiton, and for this reason is generally designated as Turkish geranium oil. The odor of the oil is improved by shaking it with water containing lemon juice, any content of copper being thereby removed. The washed oil is then brought into shallow dishes and exposed for two or three weeks to the sun, whereby its odor becomes still more like that of rose oil. The oil thus prepared is much used for adulterating rose oil. Turkish geranium oil is also much used for the adulteration of genuine geranium oil and is itself adulterated with oil of turpentine. It is extensively employed in perfumery, especially for perfuming hair oils and pomades, and in conjunction with geranium oils for rose soap.

East Indian geranium oil is obtained, chiefly in the Presidency of Bombay, from Andropogon Schoenantus, L. It is greenish-yellow to yellow-brown, has a specific gravity of 0.906 at 59° F., and consists mainly of geraniol (C₁₀H₁₈O). Its odor is rose-like, though modified by a lemon-like odor. It is principally used for perfuming cheaper articles.

French and African geranium oils (oleum geranii) are obtained by distillation with water from the leaves of various species of pelargonium. Many different kinds of this oil are found in commerce. The finest and most expensive are the Spanish and French geranium oils, so-called rosé, which are distinguished by their fine odor, closely resembling that of rose oil. They are derived from Pelargonium radula, and are either yellowish, brownish, or pale green, the brownish oils being preferred. It congeals at 60.8° F. and turns the plane of polarization to the right. Another good geranium oil is the African, which is chiefly prepared in Algiers from Pelargonium roseum, Wildenow, and P. odoratissimum, Aiton. It closely resembles the French oil, but turns the plane of polarization to the left.

French geranium oil is said to be frequently adulterated with fat or copaiba oil; but geranium oil being soluble in 70 per cent. alcohol, such adulterations are readily detected. Add to 5 cubic centimeters of 70 per cent. alcohol (specific gravity 0.890) at 59° to 62.5° F., 10 drops of the oil, and shake. If a clear solution results the oil is very likely unadulterated.

The so-called Turkish geranium oil is frequently found mixed with cocoanut oil. To detect this, place the oil in a test-tube in ice or a cold mixture for several hours, whereby the cocoanut oil separates as a white substance. Adulterations of upward to 20 per cent. are said to frequently occur.

Reliable tests to detect an adulteration of the better qualities of geranium oil with those of a lower grade do not exist, the odor being the only guide.

Jasmine oil or oil of jessamine, from the flowers of Jasminium officinale, L., and J. grandiflorum.—The oil is exclusively obtained by the absorption process, and is the most prized by the perfumer. It is, however, exceedingly rare on account of the enormous cost of its production. The extract of jasmine, the "essence de jasmine" of the French manufactories, is a solution of the oil, as obtained by extraction with lard or beef suet, in strong spirit of wine. The odor of jasmine oil is so peculiar that it is without comparison, and as such cannot be imitated.

Juniper oil (oleum juniperi) is obtained by distillation from the fruits of Juniperus communis, L., or juniper. The berries used for the purpose should be fully grown and fresh and bruised before being placed in the still. Unripe berries yield a smaller quantity and an oil of somewhat different properties than ripe berries. The oil obtained by distillation with steam is colorless and that by ordinary distillation yellowish, the former having a specific gravity of 0.840 to 0.860 and the latter of 0.850 to 0.900. It consists mainly of terpenes. By standing, a stearoptene is separated, which crystallizes in feathery needles from hot spirit of wine. The odor and taste of juniper oil remind one at the same time of juniper berries and oil of turpentine.

Juniper oil has a great tendency to thicken; it becomes resinous, acid and thickly fluid, formic acid being formed. It should be kept in well-closed bottles, and protected from light. It is frequently adulterated with oil of turpentine and juniper-wood oil. It may be tested by its behavior towards alcohol, as well as by the taste. A drop of the oil rubbed up with sugar, and shaken with 500 grammes of water, should not impart an acrid taste to the water. Juniper oil gives a clear solution with ½ part absolute alcohol; by a larger quantity it is rendered turbid.

Lavender oil (oleum lavandulæ.)—Large quantities of this oil are distilled in Southern France, in the neighborhood of Grasse and Nimes, from the flowers of lavandula officinalis, Chaix, which grows wild in that region. It is limpid, colorless, or yellowish, has a strong odor and a pungent, aromatic, somewhat bitter taste. With 90 per cent. alcohol it mixes clear in every proportion, boils at 320° F., and has a specific gravity of 0.876 to 0.905. It turns the plane of polarization to the left.

The best French lavender oil, distilled from pure flowers only, is brought into commerce under the name, "Essence de Lavande Montblanc." It is distinguished from all other kinds, in the preparation of which more or less stems and leaves are used, by its extremely agreeable odor.

Lavender is also extensively cultivated in Mitchan and Hitchin, England, and used for the preparation of an especially fine oil, the odor of which surpasses even that of the best French product. It is, however, comparatively expensive.

From the leaves and flowers of lavandula spica the spike oil is obtained by distillation. It is colorless, or yellow, and in odor approaches rosemary oil more than lavender oil. Its boiling point, like that of lavender oil, is at 366.8° F., and its specific gravity 0.96. Spike oil turns the plane of polarization only slightly to the left, the deviation scarcely ever exceeding 0.8°.

Lavender oils are very sensitive to light and air, they becoming ozonized under their influence, and acquire an odor like turpentine. Hence they must be kept in well-closed vessels in a dark place.

Oil of lavender is frequently adulterated, chiefly with alcohol, fat oils, oil of turpentine, and spike oil. To test the oil, mix a drop of it with 10 cubic centimeters of warm water, and test the odor, which should be pure and agreeably lavender-like. The taste of the vigorously agitated water should be transiently bitter aromatic. One volume of the oil should give a turbid mixture with one volume of dilute alcohol (specific gravity 0.895), but a perfectly clear one with three volumes. On shaking 0.5 cubic centimeter of the oil with a few grains of rosaniline it remains uncolored, but, in the presence of even a trace of alcohol, it acquires a red coloration. By mixing in a graduated cylinder equal volumes of the oil and distilled water, and shaking vigorously, the oil, after the water has settled, shows a decrease in volume if alcohol be present. The presence of fat oil can be readily recognized by bringing a drop of the oil to be tested upon filtering paper; a grease stain is formed, which disappears neither at the ordinary temperature nor by heating. Adulteration with oil of turpentine is recognized by the boiling point, that of oil of turpentine being 312.8° F., and that of oil of lavender, as previously stated, 366.8° F.

Spike oil should mix clear with equal parts of 90 per cent. alcohol; the contrary would indicate adulteration with oil of turpentine.

For perfumery, lavender oil is of great importance, it being much employed by itself, as well as mixed with other oils.

Lemon oil (oleum limonis) is obtained by various processes from the rinds of lemons. The best and most delicately-scented oil is obtained by the so-called sponge process in use in Southern Italy and Sicily. The rinds are soaked from fifteen to twenty-five minutes in water, to which sometimes a little soda is added. They are taken up singly in the right hand and the outer surface of each is firmly pressed against a large and rather hard-grained sponge held in the left hand and secured by a strap. Two or three sharp turns of the wrist impart what may be called a screw-pressure to the rind, thus effectually fracturing the oil cells, the sponge absorbing the contents. The sponge is constantly held over an earthen jar and occasionally squeezed into it. The fluid in the jar quickly separates into three different products—the dregs or deposit of mucilaginous and cellular matter, some fruit juice, and the pure oil, which floats on the top. The latter, when bright and clear, is passed, by means of a small glass siphon, into the cans of thin copper, in which, after sealing, it is stored away for export.

The above described primitive mode of fabrication furnishes the most highly prized oils of commerce; they are called hand-pressed oils or essences preparées a l'éponge. In the same manner are obtained the oils from the sweet and bitter pomegranate, the bergamotte, and mandarin orange.

Another method of expressing the oil is that of the écuelle à piquer, much used in the region about Nice. The oils obtained by this method, which are also of a very fine quality, are marked essence à l'écuelle or au zeste. The apparatus consists of a round shallow pan of copper or brass, having a receptacle for the oil at its lowest part and a lip on one side for pouring, and studded on its concavity by strong blunt spikes. The workman takes the fruit and rolls it gently but quickly around the inside of the écuelle; the spikes prick the oil sacs, whereupon the oil, running down the spikes and the concavity of the pan, collects in the reservoir at the lowest part. The oil is filtered and then poured into clean glass bottles, in which the impurities are allowed to settle.

In Reggio, where especially much bergamot oil is manufactured, sheet-metal bowl-like vessels, studded inside with sharp ribs, are used. Six to eight fruits are placed in the vessel. A movable lid closes the vessel, so that there is just enough space for the fruits between the lid and the bottom of the vessel. If now the lid be revolved by hand-or steam-power, the rinds of the fruit are torn apart, and the oil together with the juice runs through the sieve-bottom of the apparatus into a cylindrical vessel where it clarifies.

The third method of obtaining the oil is by expression. The grated rind is placed in hair mats, and subjected to powerful pressure by means of a screw or lever press.

The process of distillation is carried on as follows: The peels, which should be from select fruit, are sprinkled with powdered salt, and a few hours afterwards sufficient water to moisten them is poured over them. A day or two afterwards more water is added, and the whole is distilled until either no more oil separates or the steam, at first purely fragrant, begins to acquire a rank and rather unpleasant smell. The oil obtained by distillation is inferior to the others.