Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 75

=Oil, Shale.= See OILS, MINERAL.

=Oil of Soot.= _Syn._ OLEUM FULIGINIS (Ph. L. 1746), L. From wood-soot.

Fetid; reputed antispasmodic and nervine.

=Oil of Tar.= _Syn._ SPIRIT OF T.; OLEUM PINI, O. P. RUBRUM, O. TaeDae, O.

PICIS LIQUIDae, L. By simple distillation from wood-tar. Reddish and strong scented. By one or more rectifications it becomes colourless and limpid.

It soon gets thick. Used in ringworm and several other skin diseases, made into an ointment with lard. It is poisonous if swallowed in large doses.

=Oil of Tobac'co (Empyreumatic).= _Syn._ OLEUM TABACI EMPYREUMATIc.u.m (Ph.

U. S.), L. From tobacco, in coa.r.s.e powder, gradually heated in a green-gla.s.s retort to dull redness, and kept at that temperature as long as any oil pa.s.ses over; the oily portion is then separated from the water in the receiver, and kept for use. Highly narcotic and poisonous.

=Oil of Wax.= _Syn._ OLEUM CERae, L. From beeswax and sand distilled together; the product is rectified once or oftener. Reputed diuretic.--_Dose_, 3 to 6 drops.

=OILS (Fixed).= _Syn._ FAT OILS, UNCTUOUS O.; OLEA FIXA, O. EXPRESSA, L.; HUILES GRa.s.sES, Fr. The fixed oils are compounds of carbon, hydrogen, and oxygen (oxyhydro-carbons), obtained from the organic kingdom, and characterised by their insipidity, unctuosity, insolubility in water, and being lighter than that fluid. Olive oil, which is obtained from the vegetable kingdom, and spermaceti oil, which is obtained from the animal kingdom, may be taken as types of the rest.

The fixed oils are chiefly found in the fruit and seeds of plants, and in thin membranous cells, forming what is called the adipose tissue, in the bodies of animals. According to their consistence, they may be cla.s.sed into 'OILS,' 'b.u.t.tERS,' and 'TALLOWS,'

_Prop., &c._ Among the best-known properties of the fixed oils are--the permanent stain they give to paper, which they render translucid; their non-volatility at the ordinary temperature of the atmosphere, or at that of boiling water, or, indeed, at any temperature insufficient for their decomposition; their constantly floating on the surface of water when added to it; and, lastly, their inability to mix with that fluid. Some of them, as palm oil and cocoa-nut oil, are solid at ordinary temperatures; but the majority are fluid, unless they have been considerably cooled, when they separate into two portions--the one solid, consisting chiefly of stearin, or some a.n.a.logous substance, and the other liquid, consisting chiefly of olein or elain. Nearly all of them, when exposed to the air, absorb oxygen rapidly, and either gradually harden or become rancid and nauseous. From the first are selected the 'drying oil' used by painters; the last are used as food, in cookery, and for machinery, lamps, &c. The whole of these oils, when heated to their boiling points (500 to 600 Fahr.), suffer decomposition, yielding various hydrocarbons; and when suddenly exposed to a red heat, they furnish a gaseous product (oil-gas), which was formerly employed for illumination. It is owing to this property of oil and liquid fats that candles and lamps give their light. The wick is a gas-producing apparatus in miniature. With the caustic alkalies and water the fixed oils unite to form soap. When some of these oils are absorbed by porous bodies, and thus expose a vastly increased surface to the air, they absorb oxygen with such rapidity as to generate a considerable degree of heat. Paper, tow, cotton, wool, straw, shavings, &c., slightly embued with oil, and left in a heap, freely exposed to the air or sun, often spontaneously inflame. In this way many extensive fires have arisen. The above is more particularly the case with linseed, rape, nut, and olive oil. The first, made into a paste with manganese, rapidly becomes hot, and ultimately inflames spontaneously.

The specific gravities of the fixed oils range between 865 and 970, water being 1000.

_Prep._ The fixed oils, except where otherwise directed, are obtained from the bruised or ground fruit or seed, by means of powerful pressure, in screw or hydraulic presses, and are then either allowed to clarify themselves by subsidence or are filtered. Both methods are frequently applied to the same oil. In some cases the impurities are removed by ebullition with water, and subsequent separation of the pure oil. Heat is frequently employed to increase the liquidity of the oil, and thus lessen the difficulty of its expulsion from the ma.s.s. With this object the bruised ma.s.s, placed in bags, is commonly exposed to the heat of steam, and then pressed between heated plates of metal. This is always necessary with the 'butyraceous oils.'

Another method is by boiling the bruised seed in water, and skimming off the oil as it rises to the surface. This is the plan adopted for castor oil in the West Indies.

In a few cases, for medicinal purposes, the bruised ma.s.s is mixed with 1/2 its weight, or an equal weight, of alcohol or ether, and after 24 hours'

digestion the whole is submitted to pressure, and the alcohol or ether removed by distillation at a gentle heat. The first menstruum is commonly employed for croton oil on the Continent; the second, for that of ergot of rye.

_Purif._ Several methods are adopted for refining or purifying the fixed oils, among which are the following:--

1. The oil is violently agitated along with 1-1/2 to 2% of concentrated sulphuric acid, when it a.s.sumes a greenish colour, and, after about a fortnight's repose, deposits much colouring matter, becomes paler, and burns with greater brilliancy, particularly if well washed with steam or hot water, and clarified by subsequent repose or by filtration. This answers well for most of the recently expressed vegetable oils. It also greatly improves most of the fish oils.

2. A modification of the last method is to well mix the acid with the oil, then to blow steam through the mixture for some time, and afterwards to otherwise proceed as before.

3. FISH OIL (WHALE, SEAL, &c.) is purified by--

_a._ Violently agitating it with boiling water or steam, by placing it in a deep vessel with perforated bottom, through which high pressure steam is forced for some time; it is afterwards clarified by repose, and filtered through coa.r.s.e charcoal.

_b._ The oil is violently agitated with a boiling hot and strong solution of oak bark, to remove alb.u.men and gelatin, and next with high-pressure steam and hot water; it is, lastly, dried and filtered.

_c._ The oil, gently heated, is stirred for some time with about 1% of good chloride of lime, previously made into a milk by trituration with water; about 1-1/2% of oil of vitriol, diluted with 20 times its weight of water, is then added, and the agitation renewed and maintained for at least 2 hours; it is, lastly, well washed with steam or hot water.

_d._ Mr Davidson treats the oil first with a strong solution of tan, next with water and chloride of lime, then with dilute sulphuric acid, and lastly, with hot water.

_e._ Mr Dunn's method, which is very effective, and admirable on account of its simplicity, is to heat the oil by steam to from 180 to 200 Fahr., and then to force a current of air of corresponding temperature through it, under a flue or chimney, until it is sufficiently bleached and deodorised; it is, lastly, either at once filtered or is previously washed with steam or hot water.

_f._ Another method, formerly very generally adopted and still in use, is to violently agitate the oil for some time with very strong brine, or with a mixed solution of blue vitriol and common salt, and then either to allow it to clarify by repose or to filter it through freshly burnt charcoal.

4. ALMOND, CASTOR, LINSEED, NUT, OLIVE, RAPE, and some other vegetable oils, are readily bleached by either of the following processes:--

_a._ Exposure in gla.s.s bottles to the sun's rays, on the leads or roofs of houses, or in any other suitable position, open to the south-east and south. This is the method employed by druggists and oilmen to whiten their castor and linseed oils. 14 to 21 days' exposure to the sun in clear weather during summer is usually sufficient for castor oil when contained in 2 to 4-quart pale green gla.s.s bottles (preferably the former), and covered with white gallipots inverted over them. The oil is filtered before exposing it to the light, as, if only in a slight degree opaque, it does not bleach well. Almond and olive oil are, when thus treated, apt to acquire a slight sulphurous smell; but this may be removed by filtration through a little animal charcoal, or, still better, by washing the oil with hot water.

_b._ Another method employed to decolour these oils is to heat them in a wooden, tinned, or well-glazed earthen vessel along with some dry 'filtering powder' (1 to 2 lbs. per gall.), with agitation for some time, and lastly, to filter them in the usual manner through an oil-bag. In this way the West-end perfumers prepare their 'WHITE ALMOND OIL' (OLEUM AMYGDALae ALb.u.m), and their 'WHITE OLIVE OIL' (OLEUM OLIVae ALb.u.m).

Formerly, freshly burnt animal charcoal was used for this purpose, and is still so employed by some houses.

5. Mr Bancroft refines OILS FOR MACHINERY AND LUBRICATING PURPOSES generally, by agitating them with a lye of caustic soda of the sp. gr.

12. A sufficient quant.i.ty is known to have been added when, after repose, a portion begins to settle down clear at the bottom. About 4% to 8% is commonly required for lard oil and olive oil. After 24 hours' repose the clear supernatant oil is decanted from the soapy sediment, and filtered.

6. Not only the oils above referred to, but all other oils and fats, may be rendered perfectly colourless by the use of a little chromic acid; or, what is the same, by a mixture of a solution of bichromate of pota.s.sa and sufficient sulphuric, hydrochloric, or nitric acid, to seize on all the alkali, and thus liberate the chromic acid.

7. PALM OIL and COCOA-NUT OIL are generally refined and bleached by either chromic acid or chlorine, or by heat:--

_a._ The 'butyraceous oil' is liquefied by heat in a wooden vessel, and 7% to 9% of good chloride of lime, previously made into a smooth cream with water, is added, and the whole a.s.siduously stirred until the ingredients appear united; the mixture is then allowed to cool, and is next cut up into small lumps, which are exposed to a free current of air for 2, 3, or even 4 weeks; these are melted in a wooden vessel heated by high-pressure steam circulating through leaden pipes, or in a cast-iron boiler lined with lead, and an equal weight of oil of vitriol (diluted with about 20 times its weight of water) is poured in, and the whole gently boiled until the oil is discoloured and runs clear; the fire is then moderated, and the whole allowed to settle; lastly, the fire is removed, and the oil is left to cool very slowly.

_b._ The process with chromic acid has been already noticed, but is more fully explained _below_.

_c._ The oil, heated to the temperature of about 250 Fahr., is exposed to the action of high-pressure steam, which is continuously 'blown' through it for 10 or 12 hours, or even longer. The process is greatly facilitated by the introduction of some chromic acid.

8. Mr Watt's methods of purifying fats and oils are very effective, more especially for those intended for illumination. They are as follows:--

_a._ (For FISH OILS.) Each ton is boiled for 1/2 an hour with caustic soda, 1/2 lb., previously made into a weak lye with water; or steam is blown through the mixture for a like period; oil of vitriol, 1/2 lb., diluted with 6 times its weight of water, is next added, the whole again boiled for 15 minutes, and allowed to settle for an hour or longer, when the clear oil is run off from the water and sediment into the bleaching tubs; here solution of bichromate of potash, 4 lbs., in oil of vitriol, 2 lbs., previously diluted with water, q. s., together with a little nitric acid and some oxalic acid, are added, and after thorough admixture of the whole, by blowing steam through it, strong nitric acid, 1 lb., diluted with water, 1 quart, is poured in, and the boiling continued for 1/2 an hour longer; a small quant.i.ty of naphtha or rectified spirit of turpentine is then mixed in, and the oil is, finally, well washed with hot water, and left to settle.

_b._ (For PALM OIL.) The oil is melted by the heat of steam, and, after it has settled and cooled down to about 130 Fahr., is carefully decanted from the water and sediment into the steaming tubs; here a mixture of a saturated solution of bichromate of potash, 25 lbs., and oil of vitriol, 8 or 9 lbs., is added, and after thorough admixture, hydrochloric acid, 50 lbs., is poured in; the whole is then constantly stirred until it acquires a uniform greenish colour, or is sufficiently decoloured, a little more of the bleaching materials being added if the latter is not the case, after which it is allowed to repose for half an hour to settle; it is next run into a wooden vat, where it is washed, &c., as before.

_c._ (For VEGETABLE OILS.) These are treated with a solution of chromic acid, or with a solution of bichromate of pota.s.sa, or some mineral acid, as noticed at No. 6. For COLZA, LINSEED, MUSTARD, NUT, and RAPE OIL, a little hydrochloric acid is added; but for ALMOND, CASTOR, OLIVE OIL, and POPPY OIL, no such addition (at least in excess) is required.

9. RANCID OILS and FATS are recovered by boiling them for about 15 minutes with a little water and calcined magnesia; or, by filtering them through freshly burnt charcoal.

In reference to the above processes, it may be useful to remark, that chlorine, the common bleacher and deodoriser of other substances, cannot be well employed directly in the purification of oils, as certain chemical reactions occur when these substances are brought together, which increase the colour instead of removing it, and are often otherwise injurious. The same remarks apply to the use of the 'chlorides,' which frequently fails in unskilful hands, and is, indeed, of questionable utility, except, perhaps, in the case of palm oil. Even charcoal exerts little of its usual energy on the oils, and whilst it removes or lessens their offensive odour, sometimes increases their colour. The addition of 1% or 2% of very pure and recently rectified naphtha or oil of turpentine (camphine) to lamp oil is a real improvement, since it increases its combustibility and its illuminative power.

OILS FOR MEDICAL PURPOSES, as CASTOR OIL, COD-LIVER OIL &c., must not be subjected to any process beyond mere clarification by subsidence, filtration through Canton flannel or porous paper, or, at the utmost, washing with warm water, as otherwise their active and valuable properties, if not wholly removed, will be considerably lessened. See FILTRATION.

_Purity._ The fixed oils vary greatly in their value, and hence the constant inducement which leads the unprincipled dealer to adulterate the more expensive ones with those of a similar character, but of an inferior kind of grade. Various methods are adopted to detect these frauds, among which the following are the most valuable of those capable of general application. Others referring to individual oils will be found under the respective heads.

1. (From the odour.) The method of applying this test is to heat a few drops of the oil under examination in a small porcelain, platinum, or silver spoon or capsule (a watch-gla.s.s answers well), and to carefully compare the odour evolved with that arising from a known pure sample of the same kind and quality of the oil similarly treated. The odour of the two, when each is pure, is precisely alike, and immediately suggests the plant or animal from which it has been obtained. The presence of LINSEED, NUT, RAPE, SEAL, TRAIN, or WHALE OIL, is thus readily detected, and the imperfections of the sample, even if pure, rendered much more perceptible.

2. (From the density.)--_a._ According to M. Penot, every oil supposed to come from the same plant, or the same animal, has its own particular density, which, at the same temperature, never deviates more than a few thousandths. To apply this test, the relative density or specific gravity of the sample must be determined. This may be done by means of a thousand-grain bottle or an ordinary 'AREOMETER,' or, more conveniently, by an 'ELAOMETER' or 'OLEOMETER,' constructed and graduated for the purpose. 'Fischer's ELAOMETER' or 'OIL-BALANCE' is much employed on the Continent for this purpose, and is a very useful instrument. On the large scale, the weight of an accurately measured imperial gallon of the oil may be taken.

_b._ M. Lauret, an eminent Parisian chemist, a short time since observed that the variations of the density of an oil from adulteration are rendered much more apparent when it is examined in a heated state. To render this discovery practically available, he plunges an 'elaometer,'

graduated for the given temperature, into a small tin cylinder nearly filled with the oil, and then places this in a vessel containing boiling water; as soon as the whole has acquired a uniform temperature, he observes the point on the scale of the instrument at which it floats. This point for--

Colza oil is 0 Fish oil 83 Poppy oil 124 Hemp-seed oil 136 Linseed oil 210

_c._ By employing a specific gravity bottle or small gla.s.s globe, fitted with a stopper in which is hermetically fixed a capillary tube of about 8 or 9 inches in length, we may apply the above principle of M. Lauret with the greatest accuracy. This little apparatus is filled with the oil, and then immersed in boiling water for a sufficient length of time for it to acquire that temperature; it is then removed and weighed. The smallest adulteration is, it is said, in this way immediately detected.

When the density of the given sample has been taken, and the name of the oil used to adulterate it is known, the quant.i.ty of the latter present may be approximately determined from the specific gravities by the common method of alligation.[49]

[Footnote 49: See MIXTURES, Arithmetic of.]