O._A Dictionary of Arts, Manufactures and Mines containing a clear exposition of their principles and practice

OAK BARK. See TAN.

OATS. (_Avoine_, Fr.; _Hafer_, Germ.) The composition of oats is less

known than that of the other _Cerealia_. Vogel found that 100 parts of

oats afforded 66 parts of flour or meal, and 34 parts of bran; but this

proportion would depend upon the quality of the grain. The flour

contains, 2 parts of a greenish-yellow fat oil; 8·25 of bitterish sweet

extractive; 2·5 of gum; 4·30 of a gray substance, more like coagulated

albumen than gluten; 59 of starch; 24 of moisture (inclusive of the

loss). Schrader found in the ashes of oats, silica, carbonate of lime,

carbonate of magnesia, alumina, with oxides of manganese and iron.

OBSIDIAN, is a glassy looking mineral, with a large conchoidal fracture,

and of a blackish colour, which froths much at the blow-pipe before it

melts into a white enamel.

OCHRE, _yellow and brown_ (_Ocre_, Fr.; _Ocker_, Germ.); is a native

earthy mixture of silica and alumina, coloured by oxide of iron, with

occasionally a little calcareous matter and magnesia. Ochre occurs in

beds some feet thick, which lie generally above the oolite, are covered

by sandstone and quartzose sands more or less ferruginous, and are

accompanied by gray plastic clays, of a yellowish or reddish colour; all

of them substances which contribute more or less to its formation. The

ochry earths are prepared for use by grinding under edge millstones, and

elutriation. The yellow ochres may be easily rendered red or reddish

brown by calcination in a reverberatory oven, which oxidizes their iron

to a higher degree.

Native red ochre is called red chalk and reddle in England. It is an

intimate mixture of clay and red iron ochre; is massive; of an earthy

fracture; is brownish-red, blood-red, stains and writes red. The oxide

of iron is sometimes so considerable, that the ochre may be reckoned an

ore of that metal.

The ochre beds of England are in the iron sand, the lowest of the

formations which intervene between the chalk and oolites. Beds of

fuller’s earth alternate with the iron sand. The following is a section

of the ochre pits at Shotover Hill, near Oxford:--

Beds of highly ferruginous grit, forming the

summit of the hill 6 feet.

Gray sand 3 do.

Ferruginous concretions 1

Yellow sand 6

Cream-coloured loam 4

Ochre 0 6 inches.

Beneath this, there is a second bed of ochre, separated by a thin bed of

clay.

Bole, or Armenian bole; called also Lemnian earth, and terra sigillata,

because when refined it was stamped with a seal; is massive, with a

conchoidal fracture, a feeble lustre, reddish-yellow or brown, a greasy

feel; adheres to the tongue, spec. gray. 1·4 to 2·0. It occurs in the

island Stalimene (the ancient Lesbos), and in several other places,

especially at Sienna; whence the brown pigment called _terra di Siena_.

OILS (_Huiles_, Fr.; _Oele_, Germ.); are divisible into two great

classes: the fat or fixed oils, _huiles grasses_, Fr.; _Fette oele_,

Germ.; and the essential or volatile oils, _Huiles volatiles_, Fr.;

_Flüchtige_, _aetherische oele_, Germ. The former are usually bland and

mild to the taste; the latter hot and pungent. The term distilled,

applied also to the last class, is not so correct, since some of them

are obtained by expression, as the whole of the first class may be, and

commonly are.

All the known fatty substances found in organic bodies, without

reference to their vegetable or animal origin, are, according to their

consistence, arranged under the chemical heads of oils, butters, and

tallows. They all possess the same ultimate constituents, carbon,

hydrogen, and generally oxygen, and in nearly the same proportions.

The fat oils are widely distributed through the organs of vegetable and

animal nature. They are found in the seeds of many plants, associated

with mucilage, especially in those of the bicotyledinous class,

occasionally in the fleshy pulp surrounding some seeds, as the olive;

also in the kernels of many fruits, as of the nut and almond tree, and

finally in the roots, barks, and other parts of plants. In animal

bodies, the oily matter occurs enclosed in thin membranous cells,

between the skin and the flesh, between the muscular fibres, within the

abdominal cavity in the omentum, upon the intestines, and round the

kidneys, and in a bony receptacle of the skull of the spermaceti whale;

sometimes in special organs, as of the beaver; in the gall-bladder, &c.,

or mixed in a liquid state with other animal matters, as in the milk.

Braconnot, but particularly Raspail, have shown that animal fats consist

of small microscopic, partly polygonal, and partly reniform particles,

associated by means of their containing sacs. These may be separated

from each other by tearing the recent fat asunder, rinsing it with

water, and passing it through a sieve. The membranes being thus

retained, the granular particles are observed to float in the water, and

afterwards to separate, like the globules of starch, in a white

pulverulent semi-crystalline form. The particles consist of a strong

membranous skin, enclosing _stearine and elaine_, or solid and liquid

fat, which may be extracted by trituration and pressure. These are

lighter than water, but sink readily in spirit of wine. When boiled in

strong alcohol, the oily principle dissolves, but the fatty membrane

remains. These granules have different sizes and shapes in different

animals; in the calf, the ox, the sheep, they are polygonal, and from

1/70 to 1/450 of an inch in diameter; in the hog they are kidney-shaped,

and from 1/70 to 1/140 of an inch; in man, they are polygonal, and from

1/70 to 1/900 of an inch; in insects they are usually spherical, and not

more than 1/600 of an inch.

The following is a list of the Plants which yield the ordinary Unctuous

Oils of commerce:

+---+--------------------------------+---------------------+--------+

+---+--------------------------------+---------------------+--------+

| 1.|Linum usitatissum et perenne D.|Linseed oil | 0·9347 |

| 2.|Coryleus avellana } D.|Nut oil | 0·9260 |

| 3.|Juglans regia } | | |

| 4.|Papaver somniferum D.|Poppy oil | 0·9243 |

| 5.|Cannabis sativa D.|Hemp oil | 0·9276 |

| 7.|Olea Europea G.|Olive oil | 0·9176 |

| 8.|Amygdalus communis G.|Almond oil | 0·9180 |

|10.|Cucurbita pepo, and melapepo D.|Cucumber oil | 0·9231 |

|11.|Fagus silvatica G.|Beech oil | 0·9225 |

|12.|Sinapis nigra et arvensis G.|Oil of mustard | 0·9160 |

|13.|Helianthus annuus et perennis D.|Oil of sunflower | 0·9262 |

|14.|Brassica napus et campestris G.|Rape seed oil | 0·9136 |

|15.|Ricinus communis D.|Castor oil | 0·9611 |

|16.|Nicotiana tabacum et rustica D.|Tobacco seed oil | 0·9232 |

|17.|Prunus domestica G.|Plum kernel oil | 0·9127 |

|18.|Vitis vinifera D.|Grape seed oil | 0·9202 |

|19.|Theobroma cacao G.|Butter of cacao | 0·892 |

|21.|Cocus butyracea vel avoira | | |

|24.|Vateria indica G.|Piney tallow | 0·926 |

|25.|Hesperis matronalis D.|Oil of Julienne | 0·9281 |

|26.|Myagrum sativa D.|Oil of camelina | 0·9252 |

|27.|Reseda luteola D.|Oil of weld-seed | 0·9358 |

|28.|Lepidium sativum D.|Oil of garden cresses| 0·9240 |

| | |nightshade | 0·9250 |

|31.|Brassica campestris oleifera G.|Colza oil | 0·9136 |

|32.|Brassica præcox G.|Summer rapeseed oil | 0·9139 |

|33.|Raphanus sativus oleifer G.|Oil of radish seed | 0·9187 |

|34.|Prunus cerasus G.|Cherry-stone oil | 0·9239 |

|36.|Euonymus Europæus G.|Spindle tree oil | 0·9380 |

| | |cyper grass | 0·9180 |

|39.|Hyosciamus niger G.|Henbane seed oil | 0·9130 |

|40.|Æsculus hippocastanum G.|Horse chesnut oil | 0·927 |

|41.|Pinus abies D.|Pinetop oil | 028 5 |

+---+--------------------------------+---------------------+--------+

The fat oils are contained in that part of the seed which gives birth to

the cotyledons; they are not found in the plumula and radicle. Of all

the families of plants, the cruciform is the richest in oleiferous

seeds; and next to that, are the drupaceæ, amentaceæ, and solaneæ. The

seeds of the gramineæ and leguminosæ contain rarely more than a trace of

fat oil. One root alone, that of the _cyperus esculenta_, contains a fat

oil. The quantity of oil furnished by seeds varies not only with the

species, but in the same seed, with culture and climate. Nuts contain

about half their weight of oil; the seeds of the _brassica oleracea and

campestris_, one third; the variety called colza in France, two fifths;

hempseed, one fourth; and linseed from one fourth to one fifth.

Unverdorben states that a last, or ten quarters, of linseed, yields 40

ahms = 120 gallons English of oil; which is about 1 cwt. of oil per

quarter.

The fat oils, when first expressed without much heat, taste merely

unctuous on the tongue, and exhale the odour of their respective plants.

They appear quite neutral by litmus paper. Their fluidity is very

various, some being solid at ordinary temperatures, and others remaining

fluid at the freezing point of water. Linseed oil indeed does not

congeal till cooled from 4° to 18° below 0° F. The same kind of seed

usually affords oils of different degrees of fusibility; so that in the

progress of refrigeration one portion concretes before another.

Chevreul, who was the first to observe this fact, considers all the oils

to be composed of two species, one of which resembles _suet_, and was

thence styled by him _stearine_; and another which is liquid at ordinary

temperatures, and was called _elaine_, or _oleine_. By refrigeration and

pressure between the folds of blotting paper, or in linen bags, the

fluid part is separated, and the solid remains. By heating the paper in

water, the liquid oil may be obtained separate. When alcohol is boiled

with the natural oil, the greater part of the stearine remains

undissolved.

Oleine may also be procured by digesting the oil with a quantity of

caustic soda equal to one half of what is requisite to saponify the

whole; the stearine is first transformed into soap, then a portion of

the oleine undergoes the same change, but a great part of it remains in

a pure state. This process succeeds only with recently expressed or very

fresh oils. The properties of these two principles of the fat oils vary

with the nature of the respective oils, so that the sole difference does

not consist, as many suppose, in the different proportions of these two

bodies, but also in peculiarities of the several stearines and oleines,

which, as extracted from different seeds, solidify at very different

temperatures.

In close vessels, oils may be preserved fresh for a very long time, but

with contact of air they undergo progressive changes. Certain oils

thicken and eventually dry into a transparent, yellowish, flexible

substance; which forms a skin upon the surface of the oil, and retards

its further alteration. Such oils are said to be _drying_ or

_siccative_, and are used on this account in the preparation of

varnishes and painters’ colours. Other oils do not grow dry, though they

turn thick, become less combustible, and assume an offensive smell. They

are then called _rancid_. In this state, they exhibit an acid reaction,

and irritate the fauces when swallowed, in consequence of the presence

of a peculiar acid, which may be removed in a great measure by boiling

the oil along with water and a little common magnesia for a quarter of

an hour, or till it has lost the property of reddening litmus. While

oils undergo the above changes, they absorb a quantity of oxygen equal

to several times their volume. Saussure found that a layer of nut oil,

one-quarter of an inch thick, enclosed along with oxygen gas over the

surface of quicksilver in the shade, absorbed only three times its bulk

of that gas in the course of eight months; but when exposed to the sun

in August, it absorbed 60 volumes additional in the course of ten days.

This absorption of oxygen diminished progressively, and stopped

altogether at the end of three months, when it had amounted to 145 times

the bulk of the oil. No water was generated, but 21·9 volumes of

carbonic acid were disengaged, while the oil was transformed in an

anomalous manner into a gelatinous mass, which did not stain paper. To a

like absorption we may ascribe the elevation of temperature which

happens when wool or hemp, besmeared with olive or rapeseed oil, is left

in a heap; circumstances under which it has frequently taken fire, and

caused the destruction of both cloth-mills and dock-yards.

In illustration of these accidents, if paper, linen, tow, wool, cotton,

mats, straw, wood shavings, moss, or soot, be imbued slightly with

linseed or hempseed oil, and placed in contact with the sun and air,

especially when wrapped or piled in a heap, they very soon become

spontaneously hot, emit smoke, and finally burst into flames. If linseed

oil and ground manganese be triturated together, the soft lump so formed

will speedily become firm, and ere long take fire.

The fat oils are completely insoluble in water. When agitated with it,

the mixture becomes turbid, but if it be allowed to settle the oil

collects by itself upon the surface. This method of washing is often

employed to purify oils. Oils are little soluble in alcohol, except at

high temperatures. Castor oil is the only one which dissolves in cold

alcohol. Ether, however, is an excellent solvent of oils, and is

therefore employed to extract them from other bodies in analysis; after

which it is withdrawn by distillation.

Fat oils may be exposed to a considerably high temperature, without

undergoing much alteration; but when they are raised to nearly their

boiling point, they begin to be decomposed. The vapours that then rise

are not the oil itself, but certain products generated in it by the

heat. These changes begin somewhere under 600° of Fahr., and require for

their continuance temperatures always increasing. The products consist

at first in aqueous vapour, then a very inflammable volatile oil, which

causes boiling oil to take fire spontaneously; and next carburetted

hydrogen gas, with carbonic acid gas. In a lamp, a small portion of oil

is raised in the wick by capillarity, which being heated, boils and

burns. See ROSIN-GAS.

Several fat oils, mixed with one or two per cent. of sulphuric acid,

assume instantly a dark green or brown hue, and, when allowed to stand

quietly, deposit a colouring matter after some time. It consists in a

chemical combination of the sulphuric acid, with a body thus separated

from the oil, which becomes in consequence more limpid, and burns with a

brighter flame, especially after it is washed with steam, and clarified

by repose or filtration. Any remaining moisture may be expelled by the

heat of a water bath.

The oils combine with the salifiable bases, and give birth to the

substance called _glycerine_ (the sweet principle), and to the margaric,

oleic, and stearic acids. The general product of their combination with

potash or soda, is SOAP, which see. Caustic ammonia changes the oils

very difficultly and slowly into a soap; but it readily unites with them

into a milky emulsion called volatile liniment, used as a rubefacient

in medicine. Upon mixing water with this liquor, the oil separates in

an unchanged state. By longer contact, ammonia acts upon oils like the

other alkalis. Sea salt dissolves in small quantity in the oils, and so

does verdigris. The latter solution is green. Oils dissolve also several

of the vegetable alkalis, as morphia, cinchonia, quinia, strychia, and

delphia.

Olive oil consists of 77·2 carbon, 13·4 hydrogen, and 9·4 oxygen, in 100

parts. Spermaceti oil, by my analysis, of 78·9 carbon, 10·97 hydrogen,

and 10·13 oxygen.

Castor oil do. 74·0 10·3 15·7 azote,

Stearine of olive oil 82·17 11·23 6·30 0·30 _Saussure_.

Oleine of do. 76·03 11·54 12·07 0·35 do.

Linseed oil 76·01 11·35 12·64 do.

Nut oil 79·77 10·57 9·12 0·54 do.

Oil of almonds 77·40 11·48 10·83 0·29

De Saussure concludes that the less fusible fats contain more carbon and

less oxygen, and that oils are more soluble in alcohol, the more oxygen

they contain.

I shall now take a short view of the peculiarities of the principal

expressed oils.

_Oil of almonds_, according to Gusseron, contains no stearine; at least

he could obtain none by cooling it and squeezing it successively till it

all congealed. Braconnot had, on the contrary, said, that it contains 24

per cent. of stearine. I believe that Gusseron is right, and that

Braconnot had made fallacious experiments on an impure oil.

_Oil of colza_, is obtained from the seeds of _brassica campestris_, to

the amount of 39 per cent. of their weight. It forms an excellent lamp

oil, and is much employed in France.

The _corylus avellana_ furnishes in oil 60 per cent. of the weight of

the nuts.

_Hempseed oil_, resembles the preceding, but has a disagreeable smell,

and a mawkish taste. It is used extensively for making both soft soap

and varnishes.

_Linseed oil_, is obtained in greatest purity by cold pressure; but by a

steam heat of about 200° F. a very good oil may be procured in larger

quantity. The proportion of oil usually stated by authors is 22 per

cent. of the weight of the seed; but Mr. Blundell informs me, that, by

his plan of hydraulic pressure, he obtains from 26 to 27. In the

Encyclopædia Metropolitana, under _Oil Press_, a quarter of seed (whose

average weight is 400 lbs.) is said to yield 20 gallons of oil. Now as

the gallon of linseed oil weighs 9·3 lbs., the total product will be 186

lbs., which amounts to more than 45 per cent.--an extravagant statement,

about double the ordinary product in oil mills. Even supposing the

gallons not to be imperial, but old English, we should have upwards of

38 per cent. of oil by weight, which is still an impossible quantity.

Such are the errors introduced into respectable books, by adopting

without practical knowledge, the puffing statements of a patentee. It

dissolves in 5 parts of boiling alcohol, in 40 parts of cold alcohol,

and in 1·6 parts of ether. When kept long cool in a cask partly open, it

deposits masses of white stearine along with a brownish powder. That

stearine is very difficult of saponification.

_Mustard-seed oil._ The white or yellow seed affords 36 per cent. of

oil, and the black seed 18 per cent. The oil concretes when cooled a

little below 32° F.

_Nut oil_, is at first greenish coloured, but becomes pale yellow by

time. It congeals at the same low temperature as linseed oil, into a

white mass, and has a more drying quality than it.

_Oil of olives_, is sometimes of a greenish and at others of a pale

yellow colour. A few degrees above 32° F. it begins to deposit some

white granules of stearine, especially if the oil have been originally

expressed with heat. At 22° it deposits 28 per cent. of its weight in

stearine, which is fusible again at 68°, and affords 72 per cent. of

oleine. According to Kerwych, oleine of singular beauty may be obtained

by mixing 2 parts of olive oil with 1 part of caustic soda lye, and

macerating the mixture for 24 hours with frequent agitation. Weak

alcohol must then be poured into it, to dissolve the stearine soap,

whereby the oleine, which remains meanwhile unsaponified, is separated,

and floats on the surface of the liquid. This being drawn off, a fresh

quantity of spirits is to be poured in, till the separation of all the

oleine be completed. It has a slightly yellowish tint, which may be

removed by means of a little animal charcoal mixed with it in a warm

place for 24 hours. By subsequent nitration, the oleine is obtained

limpid and colourless, of such quality that it does not thicken with the

greatest cold, nor does it affect either iron or copper instruments

immersed in it.

There are three kinds of olive oil in the market. The best, called

virgin salad oil, is obtained by a gentle pressure in the cold; the more

common sort is procured by stronger pressure, aided with the heat of

boiling water; and thirdly, an inferior kind, by boiling the olive

residuum or _marc_, with water, whereby a good deal of mucilaginous oil

rises and floats on the surface. The latter serves chiefly for making

soaps. A still worse oil is got by allowing the mass of bruised olives

to ferment before subjecting it to pressure.

Oil of olives is refined for the watchmakers by the following simple

process. Into a bottle or phial containing it, a slip of sheet lead is

immersed, and the bottle is placed at a window, where it may receive the

rays of the sun. The oil by degrees gets covered with a curdy mass,

which after some time settles to the bottom, while itself becomes limpid

and colourless. As soon as the lead ceases to separate any more of that

white substance, the oil is decanted off into another phial for use.

_Palm oil_ melts at 117·5° F., and is said to consist of 31 parts of

stearine and 69 of oleine in 100. It becomes readily rancid by exposure

to air, and is whitened at the same time.

The oil extracted from the plucked tops of the _pinus abies_, in the

Black Forest in Germany, is limpid, of a golden yellow colour, and

resembles in smell and taste the oil of turpentine. It answers well for

the preparation of varnishes.

The _oil of plum-stones_, is made chiefly in Wurtemberg, and is found to

answer very well for lamps.

_Poppy-seed oil_, has none of the narcotic properties of the poppy

juice. It is soluble in ether in every proportion.

_Rape-seed oil_, has a yellow colour, and a peculiar smell. At 25° F. it

becomes a yellow mass, consisting of 46 parts of stearine, which fuses

at 50°, and 54 of oleine, in which the smell resides.

The _oils of belladonna seeds_, and _tobacco seeds_, are perfectly

bland. The former is much used for lamps in Swabia and Wurtemberg. The

oil-cakes of both are poisonous.

_Oil of wine-stones_, is extracted to the amount of 10 or 11 per cent.

from the seeds of the grape. Its colour is at first pale yellow, but it

darkens with age. It is used as an article of diet.

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