Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 84

_Pres._ Volatile oils should be preserved in well-closed and nearly full bottles, in the shade, and should be opened as seldom as possible. By age they darken, lose much of their odour, increase in density, and become thick and clammy. It is then necessary to distil them, by which the undecomposed portion is separated from the resin. Agitation along with animal charcoal will restore their clearness and original colour, but nothing more.

_Pur., Tests._ The essential or volatile oils of commerce are very frequently adulterated with the fatty oils, resins, spermaceti, or alcohol, or with other essential oils of a cheaper kind or lower grade.

The presence of the first three of these may be readily detected by placing a drop of the suspected oil on a piece of white paper, and exposing it for a short time to heat. If the oil is pure, it will entirely evaporate; but if adulterated with one of these substances, a greasy or translucent stain will be left on the paper. These substances also remain undissolved when the oil is agitated with thrice its volume of rectified spirit.

The presence of alcohol may be detected by agitating the oil with a few small pieces of dried chloride of calcium. These remain unaltered in a pure essential oil, but dissolve in one containing alcohol, and the resulting solution separates, forming a distinct stratum at the bottom of the vessel. When only a very little alcohol is present, the pieces merely change their form, and exhibit the action of the solvent on their angles or edges, which become more or less obtuse or rounded.

Another test for alcohol in the essential oils is the milkiness occasioned by agitating them with a little water, as well as the loss of volume of the oil when it separates after repose for a short time.

A more delicate test of alcohol in the essential oils than either of the preceding is pota.s.sium, as employed by M. Beral:--12 drops of the oil are placed on a perfectly dry watch-gla.s.s, and a piece of pota.s.sium, about the size of an ordinary pin's head, set in the middle of it. If the small fragment of metal retains its integrity for 12 or 15 minutes, no alcohol is present; but if it disappears after the lapse of 5 minutes, the oil contains at least 4% of alcohol; and if it disappears in less than 1 minute, it contains not less than 25% of alcohol.

Boettger states that anhydrous glycerin possesses the property of dissolving in alcohol, without mixing with the volatile oils. The mode of applying the glycerin is as follows:--The oil to be examined is well shaken in a graduated tube, with its own volume of glycerin (sp. gr.

125). Upon being allowed to settle, the mixture separates into two layers. The denser glycerin separates rapidly, and if the essence has been mixed with alcohol, this is dissolved in the glycerin, the augmentation in the volume of glycerin showing the proportion of alcohol present.

This species of adulteration is very common, as it is a general practice of the druggists to add a little of the strongest rectified spirit to their oils, to render them transparent, especially in cold weather. Oil of ca.s.sia is nearly always treated in this way.

The admixture of an inferior essential oil with one more costly may be best detected by pouring a drop or two on a piece of porous paper or cloth, and shaking it in the air, when, if occasionally smelled, the difference of the odour at the beginning and the end of the evaporation will show the adulteration, especially if the added substance is turpentine. The presence of the latter may also be detected by agitating the oil with rectified spirit, when it will remain undissolved.

The following method, which may also be used as a test for the presence of turpentine, is based upon its power of dissolving fats:--Take about 50 gr.

of oil of poppy in a graduated gla.s.s tube, and add an equal quant.i.ty of the sample of essential oil. Shake the mixture up thoroughly and then allow it to stand; if the essential oil be pure, the mixture becomes milky, and does not clear until after several days have pa.s.sed, whereas it will remain transparent if even so little as 5 per cent. of essence of turpentine be present.

The purity of essential oils may likewise, in many cases, be determined by taking their sp. gr.; or, with still greater accuracy and convenience, by measuring their index of refraction, as suggested by Dr Wollaston. A single drop of oil is sufficient for the application of the last method.

The adulteration of a heavy oil with a light one, or the reverse, may be detected by agitating the suspected oil with water, when, in most cases, the two will separate and form distinct strata.

Miss Crane believes that the cohesion figures afforded by the volatile oils, like those of the fixed ones, will be found useful indications of their purity. The application of her method is precisely similar to that followed in her examination of the fixed oils as already described. She finds that--

_Oil of Turpentine_, by itself, spreads instantly to the whole size of the plate (a common soup plate), and almost immediately the edge begins to break into irregular shapes, when a rapid motion takes place over the surface of the film, and there seems to be a contest between the cohesion of the oil particles and the adhesion between them and the water. The oil makes repeated efforts to gather itself closer together, when the water instantly reacts, giving a wavy appearance to the whole figure.

The play of colours at this point is beautiful, and serves to bring out the lines more perfectly. In a few seconds innumerable little holes appear over the surface, which soon are separated only by threaded lines, and the figure is like the most exquisitely fine lace.

_Oil of Cinnamon_ forms a figure not more than half the size of the last-named. In a few seconds small portions are detached, and shortly separate into distinct drops, four or five larger, and a number of smaller ones, scattered about. With mixtures in different proportions of _oil of turpentine_, the figures formed differently, taking more of the characteristics of the adulterant as it predominated.

_Oil of Nutmeg_ forms a large figure instantly, the edge showing a beaded line. It gathers itself together and spreads again, very like oil of turpentine, but the surface presents more the appearance of watered silk.

Within sixty seconds some holes appear, and in eighty more the surface is covered with them; these scarcely spread to more than a sixteenth of an inch in diameter, but from the first each is bordered with a dotted edge.

The figure lasts some time without changing materially, except the openings lengthen out into an oblong shape, remaining entirely distinct.

The play of colours is very fine. With the addition of one third of the _oil of turpentine_, the first spreading is little different, but openings appear in half the time, and the dotted border does not come as soon; in about four minutes the figure is most characteristically marked, and soon breaks up entirely, this being the distinctive difference between the pure oil and the mixture.

_Oil of Peppermint_ spreads instantly to a large figure, and in ten or fifteen seconds openings appear, which increase rapidly in size. At first they look somewhat like the last-named, but are not nearly so numerous, and the border soon is more like tiny drops. In one and a half or two minutes they begin to run together, and the figure breaks up.

With the addition of _turpentine oil_ the figure forms more slowly, and the breaking up is less rapid, but in five minutes the outlines only remain.

_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 pa.s.s 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 Vitae.= _Syn._ HUILE CEDRE BLANC, Fr. From the fresh tops of _Thuja occidentalis_, or American arbor-vitae tree. Yellow; fragrant; stimulant. Used in frictions for rheumatism. _Prod._ 1-1/2 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 ma.s.s 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 ma.s.s, 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 insp.i.s.sated and hard (resinified). In alcohol of 806 it is soluble in all proportions, but rectified spirit (838) dissolves only 42% of this oil. Sp. gr. (recent) 9768; (one year old) 9853 to 9855; (old) 9856 to 9900. The foreign oil is generally the heaviest.

Oil of aniseed is carminative and pectoral; and both itself and preparations have long been in favour with the ma.s.ses in coughs, colds, &c. In preparing it care must be taken that the temperature of the water in the receiver and refrigerator does not fall lower than about 68 Fahr.

_Prod._ (From the dried fruit of commerce) avoir. 2% (nearly). See OIL OF STAR-ANISE.

=Oil, Ap'ple.= See AMYL (Valerianate of), and ESSENCE OF APPLE.

=Oil of Ar'nica.= _Syn._ OLEUM ARNICae, O. A. RADIc.u.m, L. From the roots of _Arnica montana_. Yellowish brown. Sp gr. 940. Prod. 16 lbs. yielded 1 oz. of oil. The oil from the flowers of arnica is blue.

=Oil of Asarabac'ca.= _Syn._ OLEUM ASABI, O. ASARI LIQUIDUM, L. From the roots of _Asarum Europaeum_. Yellow; glutinous. Two butyraceous oils pa.s.s over at the same time.

=Oil of a.s.saft'ida.= _Syn._ OLEUM ASAFTIDA, L. From the gum resin.

Contains sulphur. Very fetid and volatile.

=Oil of Balm.= _Syn._ OLEUM MELISSae, L. From the herb (_Melissa officinalis_). Pale yellow; fragrant. Sp. gr. 970 to 975. _Prod._ 100 lbs. of the fresh flowering herb yielding 1/4 oz. of oil (M. Raybaud). A mixture of oil of lemons and rosemary is commonly sold for it.

=Oil of Balsam of Peru.= See CINNAMEINE.

=Oil of Ber'gamot.= _Syn._ BERGAMOT, ESSENCE OF B.; OLEUM BERGAMII, O.

BERGAMOTae, L. By expression from the yellow portion of the rind of the fruit of _Citrus Bergamia_, or bergamot orange. Pale greenish yellow; highly fragrant. It is obtained purer by distillation, but its perfume is then slightly less delicate. Sp. gr. 875 to 885. _Prod._ The rind of 100 bergamot oranges yielded by distillation nearly 3 oz. of oil. (M.

Raybaud.)

Oil of bergamot is frequently adulterated with rectified spirit, or with the oils of lemons, oranges, or turpentine. The presence of these substances may be detected in the manner explained under OILS (Volatile), _Purity and Tests_ (_ante_), as well as by the altered density of the oil.

Pure bergamot oil is much more soluble in rectified spirit than either of the others, and is further distinguished from them by its free solubility in solution of pota.s.sa, forming a clear solution.

=Oil of Bit'ter Almonds.= _Syn._ ESSENCE OF B. A.; OLEUM AMYGDALae AMARae, O. A. ESSENTIALE, L. From the ground cake of bitter almonds from which the fixed oil has been expressed. The common plan is to soak the cake (crumbled to fragments) for about 24 hours in twice its weight of water, to which 1/3rd or 1/4th of its weight of common salt has been added, and then to submit the whole to distillation, allowing the first half of the water that pa.s.ses over to deposit its oil, and to run back again into the still. Pale golden yellow; colourless when rectified; tastes and smells strongly nutty, like peach-kernels. It consists of 85% to 90% of hydride of benzoyl and 8% to 12% of hydrocyanic acid, with a variable quant.i.ty of benzoic acid and benzoin. The density varies a little with the age of the oil, and the temperature and rapidity with which it has been distilled.

Sp. gr. (recent) 10525; (trade crude oil) 1079 (G. Wippel); (old) 1081 (10836--Pereira). "Essential oil of almonds, free from adulteration, should have a sp. gr. at most of 1052." (Ure.) According to Prof.

Redwood, the density may vary from 10524 to 10822. The light oil contains the most hydride of benzoyl, and the heavy oil the most benzoin.

_Prod._ From less than 2 to 5%.

_Pur._ This oil is generally adulterated with cheaper oils, and in nearly every case with alcohol. When it is pure--Mixed with oil of vitriol, it strikes a clear crimson-red colour, without visible decomposition,--Mixed with an alcoholic solution of pota.s.sa, crystals are eliminated.--Iodine dissolves only partially and slowly in it, without further visible results.--Chromate of pota.s.sa does not affect it.--Nitric acid (sp. gr.

142) causes no immediate reaction, and in the course of 3 or 4 days crystals of benzoic acid begin to appear; but if only 8% or 10% of alcohol or rectified spirit is present, a violent effervescence speedily commences, and nitrous fumes are evolved. By using nitric acid, sp. gr.

15, the smallest quant.i.ty of alcohol may be detected.

_Obs._ This oil does not pre-exist in the almond, but is formed by the action of water on a peculiar crystallisable substance, called amygdalin.

It is essentially the hydride of benzoyl, but it always contains a portion of hydrocyanic or prussic acid, to which it owes its very poisonous properties. It is occasionally employed as a subst.i.tute for hydrocyanic acid in medicine; but its princ.i.p.al consumption is as a flavouring ingredient and a perfume by cooks, confectioners, liquoristes, and perfumers. For this purpose it is dissolved in rectified spirits. See ESSENCE.--_Dose_, 1/4 to 1 drop.