O.

NITROGEN, DEUTOXIDE OF;Nitrous gas,Nitric oxide(Deutoxide d’azote, Fr.;Stickstoffoxyd, Germ.); is a gaseous body which may be obtained by pouring upon copper or mercury, in a retort, nitric acid of moderate strength. The nitrous gas comes over in abundance without the aid of heat, and may be received over water freed from air, or over mercury, in the pneumatic trough. It is elastic and colourless; what taste and smell it possesses are unknown, because the moment it is exposed to the mouth or nostrils, it absorbs atmospherical oxygen, and becomes nitrous or nitric acid. Its specific gravity is 1·0393, or 1·04; whence 100 cubic inches weigh 36·66 gr. Water condenses not more than1⁄20of its volume of this gas. It extinguishes animal life, and the flame of many combustibles; but of phosphorus well kindled, it brightens the flame in a most remarkable degree. It consists of 47 parts of nitrogen gas, and 53 of oxygen gas,by weight; and of equal parts in bulk, without any condensation; so that the specific gravity of deutoxide of nitrogen is the arithmetical mean of the two constituents. The constitution of this gas, and the play of affinities which it exercises in the formation of sulphuric acid, are deeply interesting to the chemical manufacturer.The Hyponitrous acid(Salpetrigesaüre, Germ.), like the preceding compound, deserves notice here, on account of the part it plays in the conversion of sulphur into sulphuric acid, by the agency of nitre. It is formed by mingling four volumes of deutoxide of nitrogen with one volume of oxygen; and appears as a dark orange vapour which is condensable into a liquid at a temperature of 4° -zero, Fahr. When distilled, this liquid leaves a dark yellow fluid. The pure hyponitrous acid consists of 37·12 nitrogen, and 62·88 oxygen; or of two volumes of the first, and three of the second. Water converts it into nitric acid and deutoxide of nitrogen; the latter of which escapes with effervescence. This acid oxidizes most combustible bodies with peculiar energy and though its vapour does not operate upon dry sulphurous acid, yet, through the agency of steam it converts it into sulphuric acid, itself being simultaneously transformed into deutoxide of nitrogen; ready to become hyponitrous acid again, and to perform a circulating series of important metamorphoses. SeeSulphuric Acid.

The Hyponitrous acid(Salpetrigesaüre, Germ.), like the preceding compound, deserves notice here, on account of the part it plays in the conversion of sulphur into sulphuric acid, by the agency of nitre. It is formed by mingling four volumes of deutoxide of nitrogen with one volume of oxygen; and appears as a dark orange vapour which is condensable into a liquid at a temperature of 4° -zero, Fahr. When distilled, this liquid leaves a dark yellow fluid. The pure hyponitrous acid consists of 37·12 nitrogen, and 62·88 oxygen; or of two volumes of the first, and three of the second. Water converts it into nitric acid and deutoxide of nitrogen; the latter of which escapes with effervescence. This acid oxidizes most combustible bodies with peculiar energy and though its vapour does not operate upon dry sulphurous acid, yet, through the agency of steam it converts it into sulphuric acid, itself being simultaneously transformed into deutoxide of nitrogen; ready to become hyponitrous acid again, and to perform a circulating series of important metamorphoses. SeeSulphuric Acid.

NITROGEN GAS, or AZOTE (Eng. and Fr.;Stickstoffgas, Germ.); constitutes about 79 hundredths of the bulk of the atmospheric air; it is copiously disengaged from several mineral springs, as from the natural basins of hot water which supply the baths of Leuk, near the Gemmi in Switzerland, and from other springs, in the Pyrenees, in Ceylon, South and North America, &c. It exists also in flesh and most animal substances, as well as in some vegetable products, being one of their essential constituents. When phosphorus is burnt within a jar filled with air, standing over water in the pneumatic trough, it consumes or absorbs the oxygen, and leaves nitrogen, which may be rendered pure by agitation with water. By exposing nitrite of ammonia to heat in a retort, nitrogen comes over alone in great abundance; for the hydrogen of the ammonia is sufficient to saturate the oxygen of the acid, and to convert it into water; while the nitrogen of both constituents is set at liberty. By transmitting chlorine through water of ammonia, or digesting lean flesh in warm nitric acid, nitrogen may also be obtained. This permanently elastic gas is destitute of colour, taste, and smell; it has a specific gravity of 0·976, air being 1·000. Hence 100 cubic inches of it weigh 29·7 gr. It extinguishes all burning bodies, and when respired without oxygen is fatal to animal life.

NITROGEN, PROTOXIDE OF;Nitrous oxide(Protoxide d’azote, Fr.;Stickstoffoxydul, Germ.); is a gas which displays remarkable powers when breathed, causing in many persons unrestrainable feelings of exhilaration, whence it has been called the laughing or intoxicating gas. It is prepared by exposing crystallized nitrate of ammonia to a heat of about 350° Fahr., in a glass retort. It is much denser than the air of the atmosphere, having a spec. grav. of 1·527; whence 100 cubic inches weigh 46·6 grains. It consists of 63·64 parts of nitrogen, and 36·36 of oxygen, by weight; or of two volumes of nitrogen and one volume of oxygen, condensed by reciprocal attraction into two volumes. It is colourless, and possesses all the mechanical properties of the atmosphere. Water previously freed from air absorbs its own volume of this gas; and thus affords a ready criterion for estimating its freedom from incondensable gases, as oxygen, nitrogen, and its deutoxide. Several combustibles burn in this gas with an enlarged blue and very vivid flame; and it relumes a taper, which has been blown out, provided its tip be redhot. By powerful pressure it may be liquefied. SeeGas.

NITRO-MURIATIC ACID,Aqua regia(Acide nitro-muriatique, Fr.;Salpeter-salzsaüre, Königswasser, Germ.); is the compound menstruum invented by the alchemists for dissolving gold. If strong nitric acid, orange-coloured by saturation with nitrous gas (deutoxide of azote), be mixed with the strongest liquid muriatic acid, no other effect is produced than might be expected from the action of nitrous acid of the same strength upon an equal quantity of water; nor has the mixed acid so formed, any power of acting upon gold or platina. But if colourless aquafortis and ordinary muriatic acid be mixed together, the mixture immediately becomes yellow, and acquires the power of dissolving these two noble metals. When gently heated, pure chlorine gas rises from it, and its colour becomes deeper; when further heated, chlorine still rises, but now mixed with nitrous acid gas. If the process has been very long continued, till the colour becomes very dark, no more chlorine can be procured, and the liquor has lost the power of dissolving gold. It then consists of nitrous and muriatic acids. It appears, therefore, that aqua regia owes its peculiar properties to the mutual decomposition of the nitric and muriatic acids; and that water, chlorine, and nitrous acid gas are the results of that reaction. Aqua regia does not, strictly speaking, oxidize gold and platinum; it causes merely their combination with chlorine. It may be composed of very different proportions of the two acids; the nitric being commonly of specific gravity 1·34; the muriatic, of specific gravity 1·18 or 1·19. Sometimes 3 parts, and at others 6 parts of the muriatic acid are mixed with 1 of nitric; and occasionally muriateof ammonia, instead of muriatic acid, is added to nitric acid for particular purposes, as for making a solution of tin for the dyers. An aqua regia may also be prepared by dissolving nitre in muriatic acid.

NITROUS ACID (Acide nitreux, Fr.;Salpetrige salpetersaüre, Germ.), may be procured by distilling, in a coated glass retort, perfectly dry nitrate of lead, into a glass receiver surrounded with a freezing mixture. The acid passes over in vapour, and condenses into a liquid; oxygen gas escapes through the safety tube; while oxide of lead remains in the bottom of the retort. Nitrous acid may also be obtained by distilling strong fuming nitric acid, at the lowest possible temperature, and rectifying what comes over. At 4° -zero, Fahr., this acid is colourless; at 32° it is wax yellow; at 60° it has an orange hue. It possesses a strong smell, has a very pungent, acrid, sour taste, and a specific gravity of 1·42. It powerfully decomposes organic bodies, staining them yellow. It boils at 82° Fahr. with the disengagement of red or orange fumes. Its constituents are, 41·34 of hyponitrous acid, and 58·66 of anhydrous nitric acid; or ultimately, 30·68 nitrogen = 1 volume, and 69·32 oxygen = 2 volumes. In its other habitudes, it is quite analogous to hyponitrous acid.A mixture of this double or compound acid with nitric acid, constitutes the orange-brown fuming nitrous acid of the British apothecaries.The hyponitrous and nitrous are two acids remarkable for containing no water in their composition; being thereforedry liquids.

A mixture of this double or compound acid with nitric acid, constitutes the orange-brown fuming nitrous acid of the British apothecaries.

The hyponitrous and nitrous are two acids remarkable for containing no water in their composition; being thereforedry liquids.

NOPAL, is the Mexican name of the plantcactus opuntia, upon which the cochineal insect breeds.

NUTMEG (Muscade, Fr.;Muskatennuss, Germ.); is the fruit of themyristica moschata, a beautiful tree of the family of thelaurineæof Jussieu, which grows in the Molucca islands. All the parts of this tree are very aromatic; but only those portions of the fruit called mace and nutmeg are sent into the market. The entire fruit is a species ofdrupa, of an ovoid form, of the size of a peach, and furrowed longitudinally. The nutmeg is the innermost kernel, or seed, contained in a thin shell, which is surrounded by the mace; and this again is enclosed in a tough fleshy skin, which opening at the tip, separates into two valves. The nutmeg tree yields three crops annually; one in April, which is the best; one in August; and one in December.Good nutmegs should be dense, and feel heavy in the hand. When they have been perforated by worms, they feel light, and though the holes have been fraudulently stopped, the unsound ones may be easily detected by this criterion.Nutmegsafford two oily products. 1. Butter of nutmeg, vulgarly called oil of mace, is obtained in the Moluccas, by expression, from the fresh nutmegs, to the amount of 50 per cent. of their weight. It is a reddish yellow butter-like substance, interspersed with light and dark streaks, and possesses the agreeable smell and taste of the nutmeg, from the presence of a volatile oil. It consists of two fats; one reddish and soft, soluble in cold alcohol; another white and solid, soluble in hot alcohol. 2. The volatile oil is solid, or astereoptène, and has been styledMyristicine.

Good nutmegs should be dense, and feel heavy in the hand. When they have been perforated by worms, they feel light, and though the holes have been fraudulently stopped, the unsound ones may be easily detected by this criterion.

Nutmegsafford two oily products. 1. Butter of nutmeg, vulgarly called oil of mace, is obtained in the Moluccas, by expression, from the fresh nutmegs, to the amount of 50 per cent. of their weight. It is a reddish yellow butter-like substance, interspersed with light and dark streaks, and possesses the agreeable smell and taste of the nutmeg, from the presence of a volatile oil. It consists of two fats; one reddish and soft, soluble in cold alcohol; another white and solid, soluble in hot alcohol. 2. The volatile oil is solid, or astereoptène, and has been styledMyristicine.

NUT OIL. SeeOils, Unctuous.

NUX VOMICA, a poisonous nut, remarkable for containing the vegeto-alkaliStrychnia.

OAK BARK. SeeTan.

OATS. (Avoine, Fr.;Hafer, Germ.) The composition of oats is less known than that of the otherCerealia. 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 ochresmay 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 hill6feet.Gray sand3do.Ferruginous concretions1Yellow sand6Cream-coloured loam4Ochre6inches.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 calledterra di Siena.

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:—

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 calledterra 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 theessential 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, enclosingstearine 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 from1⁄70to1⁄450of an inch in diameter; in the hog they are kidney-shaped, and from1⁄70to1⁄140of an inch; in man, they are polygonal, and from1⁄70to1⁄900of an inch; in insects they are usually spherical, and not more than1⁄600of an inch.The following is a list of the Plants which yield the ordinary Unctuous Oils of commerce:No.Plants.Oils.Spe-cificgravity.1.Linum usitatissum et perenneD.Linseed oil0·93472.Coryleus avellana-D.Nut oil0·92603.Juglans regia4.Papaver somniferumD.Poppy oil0·92435.Cannabis sativaD.Hemp oil0·92766.Sesamum orientaleG.Oil of sesamum7.Olea EuropeaG.Olive oil0·91768.Amygdalus communisG.Almond oil0·91809.Guilandina mohringaG.Oil of behen or ben10.Cucurbita pepo, and melapepoD.Cucumber oil0·923111.Fagus silvaticaG.Beech oil0·922512.Sinapis nigra et arvensisG.Oil of mustard0·916013.Helianthus annuus et perennisD.Oil of sunflower0·926214.Brassica napus et campestrisG.Rape seed oil0·913615.Ricinus communisD.Castor oil0·961116.Nicotiana tabacum et rusticaD.Tobacco seed oil0·923217.Prunus domesticaG.Plum kernel oil0·912718.Vitis viniferaD.Grape seed oil0·920219.Theobroma cacaoG.Butter of cacao0·89220.Cocos nuciferaG.Cocoa nut oil21.Cocus butyracea vel avoira elaisG.Palm oil0·96822.Laurus nobilisG.Laurel oil23.Arachis hypogæaG.Ground-nut oil24.Vateria indicaG.Piney tallow0·92625.Hesperis matronalisD.Oil of Julienne0·928126.Myagrum sativaD.Oil of camelina0·925227.Reseda luteolaD.Oil of weld-seed0·935828.Lepidium sativumD.Oil of garden cresses0·924029.Atropa belladonnaD.Oil of deadly nightshade0·925030.Gossypium BarbadenseD.Cotton seed oil31.Brassica campestris oleiferaG.Colza oil0·913632.Brassica præcoxG.Summer rapeseed oil0·913933.Raphanus sativus oleiferG.Oil of radish seed0·918734.Prunus cerasusG.Cherry-stone oil0·923935.Pyrus malusG.Apple seed oil36.Euonymus EuropæusG.Spindle tree oil0·938037.Cornus sanguineaG.Cornil berry tree oil38.Cyperus esculentaG.Oil of the roots of cyper grass0·918039.Hyosciamus nigerG.Henbane seed oil0·913040.Æsculus hippocastanumG.Horse chesnut oil0·92741.Pinus abiesD.Pinetop oil028 5The 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 thecyperus 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 thebrassica 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 resemblessuet, and was thence styled by himstearine; and another which is liquid at ordinary temperatures, and was calledelaine, oroleine. 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 bedryingorsiccative, 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 calledrancid. 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. SeeRosin-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 calledglycerine(the sweet principle), and to the margaric, oleic, and stearic acids. The general product of their combination with potash or soda, isSoap, 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 inmedicine. 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 of77·2carbon,13·4hydrogen, and9·4oxygen, in 100 parts.Spermaceti oil,by my analysis, of78·9carbon,10·97hydrogen, and10·13oxygen.Castor oildo.74·010·315·7azote,Stearine of olive oil82·1711·236·300·30Saussure.Oleine ofolivdo.76·0311·5412·070·35do.Linseed oil76·0111·3512·64do.Nut oil79·7710·579·120·54do.Oil of almonds77·4011·4810·830·29De 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 ofbrassica campestris, to the amount of 39 per cent. of their weight. It forms an excellent lamp oil, and is much employed in France.Thecorylus avellanafurnishes 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, underOil 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 ormarc, 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 oilmelts 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 thepinus 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.Theoil 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.Theoils of belladonna seeds, andtobacco 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.FAT OIL MANUFACTURE.It is the practice of almost all the proprietors in the neighbourhood of Aix, in Provence, to preserve the olives for 15 days in barns or cellars, till they have undergone a species of fermentation, in order to facilitate the extraction of their oil. If this practice were really prejudicial to the product, as some theorists have said, would not the high reputation and price of the oil of Aix have long ago suffered, and have induced them to change their system of working? In fact all depends upon the degree of fermentation excited. They must not be allowed to mould in damp places, to lie in heaps, to soften so as to stick to each other, and discharge a reddish liquor, or to become so hot as to raise a thermometer plunged into the mass up to 96° F. In such a case they would afford an acrid nauseous oil, fit only for the woollen or soap manufactories. A slight fermentative action, however, is useful, towards separating the oil from the mucilage. The olives are then crushed under the stones of an edge-mill, and next put into a screw-press, being enclosed in bullrush-mat bags (cabas), laid over each other to the number of eighteen. The oil is run off from the channels of the ground-sill, into casks, or into stone cisterns calledpizes, two-thirds filled with water. The pressure applied to thecabasshould be slowly graduated.What comes over first, without heat, is the virgin oil already mentioned. Thecabasbeing now removed from the press, their contents are shovelled out, mixed with some boiling water, again put in the bags, and pressed anew. The hot water helps to carry off the oil, which is received in other casks orpizes. The oil ere long accumulates at the surface, and is skimmed off with large flat ladles; a process which is calledlever l’huile. When used fresh, this is a very good article, and quite fit for table use, but is apt to get rancid when kept. The subjacent water retains a good deal of oil, by the intervention of the mucilage; but by long repose in a large general cistern, calledl’enfer, it parts with it, and is then drawn off from the bottom by a plug-hole. The oil which remains after the water is run off, is of an inferior quality, and can be used only for factory purposes.The marc being crushed in a mill, boiled with water, and expressed, yields a still coarser article.All the oil must befinedby keeping in clean tuns, in an apartment, heated to the 60th degree Fahr. at least, for twenty days; after which it is run off into strong casks, which are cooled in a cellar, and then sent into the market.Oil of almonds, is manufactured by agitating the kernels in bags, so as to separate their brown skins, grinding them in a mill, then enclosing them in bags, and squeezing them strongly between a series of cast iron plates, in a hydraulic press; without heat at first, and then between heated plates. The first oil is the purest, and least apt to become rancid. It should be refined by filtering through porous paper. Next to olive oil, this species is the most easy to saponify. Bitter almonds being cheaper than the sweet, are used in preference for obtaining this oil, and they afford an article equally bland, wholesome, and inodorous. But a strongly scented oil may be procured, according to M. Planché, by macerating the almonds in hot water, so as to blanch them,then drying them in a stove, and afterwards subjecting them to pressure. The volatile oil of almonds is obtained by distilling the marc or bitter almond cake, along with water. SeePress, Hydraulic, andStearine.Linseed, rapeseed, poppyseed, and other oleiferous seeds were formerly treated for the extraction of their oil, by pounding in hard wooden mortars with pestles shod with iron, set in motion by cams driven by a shaft turned with horse or water power, then the triturated seed was put into woollen bags which were wrapped up in hair-cloths, and squeezed between upright wedges in press-boxes by the impulsion of vertical rams driven also by a cam mechanism. In the best mills upon the old construction, the cakes obtained by this first wedge pressure, were thrown upon the bed of an edge-mill, ground anew, and subjected to a second pressure, aided by heat now, as in the first case. These mortars and press-boxes constitute what are called Dutch mills. They are still in very general use both in this country and on the Continent; and are by many persons supposed to be preferable to the hydraulic presses.Roller-millThe roller-mill, for merely bruising the linseed, &c., previous to grinding it under edge-stones, and to heating and crushing it in a Dutch or a hydraulic oil-mill, is represented infigs.770.and771.The iron shafta, has a winch at each end, with a heavy fly-wheel upon the one of them, when the machine is to be worked by hand. Upon the opposite end is a pulley, with an endless cord which passes round a pulley on the end of the fluted rollerb, and thereby drives it. This fluted rollerb, lies across the hopperc, and by its agitation causes the seeds to descend equably through the hopper, between the crushing rollersd,e. Upon the shafta, there is also a pinion which works into two toothed wheels on the shafts of the crushing cylindersdande, thus communicating to these cylinders motion in opposite directions.f,gare two scraper-blades, which by means of the two weightsh,h, hanging upon levers, are pressed against the surfaces of the cylinders, and remove any seed-cake from them. The bruised seeds fall through the slitiof the case, and are received into a chest which stands upon the boardk.Machines of this kind are now usually driven by power. Hydraulic presses have been of late years introduced into many seed-oil mills in this country; but it is still a matter of dispute whether they, or the old Dutch oil-mill, with bags of seed compressed between wedges, driven by cam-stamps, be the preferable; that is, afford the largest product of oil with the same expenditure of capital and power. For figures of hydraulic presses, seePress, andStearine.This bruising of the seed is merely a preparation for its proper grinding under a pair of heavy edge-stones, of granite, from 5 to 7 feet in diameter; because unbruised seed is apt to slide away before the vertical rolling wheel, and thus escape trituration. The edge-mill, for grinding seeds, is quite analogous to the gunpowder-mill represented infig.531.,page 630. Some hoop the stones with an iron rim, but others prefer, and I think justly, the rough surface of granite, and dress it from time to time with hammers, as it becomes irregular. These stones make from 30 to 36 revolutions upon their horizontal bed of masonry or iron in a minute. The centre of the bed, where it is perforated for the passage of the strong vertical shaft which turns the stones, is enclosed by a circular box of cast iron, firmly bolted to the bed-stone, and furnished with a cover. This box serves to prevent any seeds or powder getting into the step or socket, and obstructing the movement. The circumference of the mill-bed is formed of an upright rim of oak-plank, bound with iron. There is a rectangular notch left in the edge of the bed, and corresponding part of the rim, which is usually closed with a slide-plate, and is opened only at the end of the operation, to let the pasty seed-cake be turned out bythe oblique arm of the bottom scraper. The two parallel stones, which are set near each other, and travel round their circular path upon the bed, grind the seeds not merely by their weight, of three tons each, but also by a rubbing motion, or attrition; because their periphery being not conical, but cylindrical, by its rolling upon a plane surface, must at every instant turn round with friction upon their resting points. Strong cast-iron boxes are bolted upon the centres of the stones, which by means of screw clamps seize firmly the horizontal iron shafts that traverse and drive them, by passing into a slit-groove in the vertical turning shaft. This groove is lined with strong plates of steel, which wear rapidly by the friction, and need to be frequently renewed.The seeds which have been burst between the rolls, or in the mortars of the Dutch mills, are to be spread as equably as possible by a shovel upon the circular path of the edge-stones, and in about half an hour the charge will be sufficiently ground into a paste. This should be put directly into the press, when fine cold-drawn oil is wanted. But in general the paste is heated before being subjected to the pressure. The pressed cake is again thrown under the edge-stones, and, after being ground the second time, should be exposed to a heat of 212° Fahr., in a proper pan, called a steam-kettle, before being subjected to the second and final pressure in the woollen bags and hair-cloths.Steam-kettle and seed-stirrersFig.772.is a vertical section of the steam-kettle of Hallette, andfig.773.is a view of the seed-stirrer.a, is the wall of masonry, upon which, and the iron pillarsb, the pan is supported. It is enclosed in a jacket, for admitting steam into the intermediate spaced,d,d, at its sides and bottom.c, is the middle of the pan in which the shaft of the stirrer is planted upright, resting by its lower end in the stepe;f, is an opening, by which the contents of the pan may be emptied;g, is an orifice into which the mouth of the hair or worsted bag is inserted, in order to receive the heated seed, when it is turned out by the rotation of the stirrer and the withdrawal of the plugffrom the discharge aperture;h, is the steam induction pipe; andt, the eduction pipe, which serves also to run off the condensed water.The hydraulic oil-press is generally double; that is, it has two vertical rams placed parallel to each other, so that while one side is under pressure, the other side is being discharged. The bags of heated seed-paste or meal are put into cast-iron cases, which are piled over each other to the number of 6 or 8, upon the press sill, and subjected to a force of 300 or 400 tons, by pumps worked with a steam engine. The first pump has usually 2 or 21⁄2inches diameter for a ram of 10 inches, and the second pump one inch. Each side of the press, in a well-going establishment, should work 38 pounds of seed-flour every 5 minutes. Such a press will do 70 quarters of linseed in the days’ work of one week, with the labour of one man at 20s.and three boys at 5s.each; and will require a 12-horse power to work it well, along with the rolls and the edge-stones.I am indebted to my excellent friend Mr. E. Woolsey, for the following most valuable notes, taken by him at sundry mills for pressing oil; and remarks upon the subject of seed-crushing in general.“The chief point of difference depends upon the quality of seed employed. Heavy seed will yield most oil, and seed ripened under a hot sun, and where the flax is not gathered too green, is the best. The weight of linseed varies from 48 to 52 lbs. per imperial bushel; probably a very fair average is 49 lbs., or 392 lbs. per imperial quarter. I inspected one of the seed-crusher’s books, and the average of 15 trials of a quarter each of different seeds in the season averaged 141⁄2galls. of 71⁄2lbs. each; say, 109 lbs. of oil per quarter. This crusher, who uses only the hydraulic press, and one pressing, informed me thatArchangel seed will yield from15 to 16 galls. (of 71⁄2lbs. each)Best Odessa18 and even 19 galls.Good crushing-seed151⁄2d even 19 gdo.Low seed, such as weighs 48 lbs. per bushel131⁄2d even 19 gdo.“The average of the seed he has worked, which he represents to be of an inferior quality, for the sake of its cheapness, yields 141⁄2galls. per quarter. I had some American seed which weighed 521⁄4lbs. per imperial bushel, ground and pressed under my own observation, and it gave me 111 lbs. oil; that is to say, 418 lbs. of seed gave 111 lbs. oil = 2656⁄100per cent. A friend of mine, who is a London crusher, told me the oil varied according to the seed from 14 to 17 galls.; and when you consider the relative value of seeds, and remember thatoilandcakefrom any kind of seed is of thesame value, it will be apparent that the yield is very different; for example,25th July, 1836,prices of seed.-E. India linseedworth52s.per quarter.Petersburg linseed48to 52do.Odessa52——The difference of 4s.must be paid for in the quantity of oil which at 38s.6d.per cwt. (the then price) requires about 111⁄2lbs. more oil expressed to pay for the difference in the market value of the seed. Another London crusher informed me that East India linseed will produce 17 gallons, and he seemed to think that that was the extreme quantity that could be expressed fromany seed. The average of last year’s Russian seed would be about 14 galls.; Sicilian seed 16 galls.Place.Engine Power.Hydraulic Presses.Stampers.Rollers.Edge-stones.Kettles.Work done,--reduced to an hour.Number of pressings.France10 horse power1 hydraulic, 200 tons.5 light stampers.1 pair rolls.1 pr. edge-stones.5 table kettles small size heated by steam.1 English quarter per working hour.2 pressings.London20 horse power1 hydraulic, 800 tons.13 light stampers.1 pair rolls.2 pr. edge-stones.8 table kettles small size heated by fire.2 English quarters per working hour.2 dittoLondon12 horse power, but the engine is used also for other work.none9 light stampers.2 pair rolls, used also for other purposes.2 pr. edge-stones, used also for other purposes.4 table kettles small size heated by fire.7⁄8English quarter per working hour.2 dittoHull18 horse engine, old construction.none3 very heavy stampers.1 pair rolls.1 pr. edge-stones.3 double case large size steam kettles.11⁄4English quarter per working hour.1 dittoDitto22 horse enginenone6 very heavy stampers.2 pair rolls.2 pr. edge-stones.6 double case large size steam kettles.Not known.1 ditto“Rape-seed.—I have not turned my attention to quantity of oil extracted from this seed; but a French crusher (M. Geremboret), on whom I think one may place considerable dependence, told me, that31⁄2lbs. ofbest Cambray rape-seed yielded1 lb. oil.33⁄4—common rape-seed1 lb. oil.41⁄4—com—onpoppy-seed1 lb. oil.“Rape-seed weighs from 52 to 56 lbs. per imperial bushel.”The following are the heads of a reference of machinery for a seed oil-mill:—1. Two pairs of cast-iron rollers, 19 inches long, and 10 inches in diameter, fixed in a cast-iron frame, with brasses, wheels, shafts, bolts, scrapers, hoppers, shoes, &c.2. Two pairs of edge-stones, 7 feet diameter each, with two bottom stones, 6 feet diameter each, cast-iron upright shafts, sweepers, wheels, shafts, chairs, brasses, bolts, and scrapers, with driving spur-wheels, &c.3. Five steam kettles, with wheels, shafts, and brasses, bolts, breeches, and steam pipes, an upright cast-iron shaft, with chairs and brasses at each end; and a large bevel wheel upon the bottom end of upright shaft, and another, smaller, upon fly-wheel shaft, for the first motions.4. Five stamper presses, with press plates of cast iron, cast-iron stamper shaft with 10 arms and 10 rollers, with bosses, brasses, bolts, driving bevel-wheels.A well made oil-mill, consisting of the above specified parts, will manufacture 200 quarters of seed per week.I have been assured by practical engineers, conversant in oil-mills, that a double hydraulic press, with 2 ten-inch rams, will do the work of no more than two of the stamper presses; that is to say, it will work 22 quarters in 24 hours; while three stamper presses will work 33 quarters in the same time, and produce one half more oil.Castor oil, quantity of,Im-ported.Retainedforconsumption.Ex-ported.Year.Cwts.Cwts.Cwts.1835.1,109,307670,20561,2961836.981,585809,55968,515Duty, from British possessions, 2s.6d.per cwt.; from foreign, 1s.per lb.Cocoa-nut oil, quantity of,Im-ported.Retainedforconsumption.Ex-ported.Year.Cwts.Cwts.Cwts.1835.19,83814,0152,2381836.26,05826,0623,1581837.41,21828,836Olive oil, quantity of,Im-ported.Retainedforconsumption.Ex-ported.Year.Cwts.Cwts.Cwts.1835.606,166554,196283,7341836.2,682,0161,844,622150,5611837.1,720,3971,499,122Duties on olive oil, not of Naples and Sicily, 4d.; of Naples and Sicily, 8d.; and, if in ships of these countries, 10d.per gallon.Train oil, spermaceti, and blubber, quantity of,Im-ported.Retainedforconsumption.Ex-ported.Year.Cwts.Cwts.Cwts.1835.24,19716,1148,0351836.19,48918,7221,3651837.21,82321,286Duties on oil taken by British ships, 1s.; by foreign fishers,£26 18s.per tun.

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, enclosingstearine 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 from1⁄70to1⁄450of an inch in diameter; in the hog they are kidney-shaped, and from1⁄70to1⁄140of an inch; in man, they are polygonal, and from1⁄70to1⁄900of an inch; in insects they are usually spherical, and not more than1⁄600of an inch.

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

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 thecyperus 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 thebrassica 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 resemblessuet, and was thence styled by himstearine; and another which is liquid at ordinary temperatures, and was calledelaine, oroleine. 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 bedryingorsiccative, 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 calledrancid. 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. SeeRosin-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 calledglycerine(the sweet principle), and to the margaric, oleic, and stearic acids. The general product of their combination with potash or soda, isSoap, 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 inmedicine. 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.

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 ofbrassica campestris, to the amount of 39 per cent. of their weight. It forms an excellent lamp oil, and is much employed in France.

Thecorylus avellanafurnishes 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, underOil 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 ormarc, 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 oilmelts 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 thepinus 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.

Theoil 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.

Theoils of belladonna seeds, andtobacco 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.

FAT OIL MANUFACTURE.

It is the practice of almost all the proprietors in the neighbourhood of Aix, in Provence, to preserve the olives for 15 days in barns or cellars, till they have undergone a species of fermentation, in order to facilitate the extraction of their oil. If this practice were really prejudicial to the product, as some theorists have said, would not the high reputation and price of the oil of Aix have long ago suffered, and have induced them to change their system of working? In fact all depends upon the degree of fermentation excited. They must not be allowed to mould in damp places, to lie in heaps, to soften so as to stick to each other, and discharge a reddish liquor, or to become so hot as to raise a thermometer plunged into the mass up to 96° F. In such a case they would afford an acrid nauseous oil, fit only for the woollen or soap manufactories. A slight fermentative action, however, is useful, towards separating the oil from the mucilage. The olives are then crushed under the stones of an edge-mill, and next put into a screw-press, being enclosed in bullrush-mat bags (cabas), laid over each other to the number of eighteen. The oil is run off from the channels of the ground-sill, into casks, or into stone cisterns calledpizes, two-thirds filled with water. The pressure applied to thecabasshould be slowly graduated.

What comes over first, without heat, is the virgin oil already mentioned. Thecabasbeing now removed from the press, their contents are shovelled out, mixed with some boiling water, again put in the bags, and pressed anew. The hot water helps to carry off the oil, which is received in other casks orpizes. The oil ere long accumulates at the surface, and is skimmed off with large flat ladles; a process which is calledlever l’huile. When used fresh, this is a very good article, and quite fit for table use, but is apt to get rancid when kept. The subjacent water retains a good deal of oil, by the intervention of the mucilage; but by long repose in a large general cistern, calledl’enfer, it parts with it, and is then drawn off from the bottom by a plug-hole. The oil which remains after the water is run off, is of an inferior quality, and can be used only for factory purposes.

The marc being crushed in a mill, boiled with water, and expressed, yields a still coarser article.

All the oil must befinedby keeping in clean tuns, in an apartment, heated to the 60th degree Fahr. at least, for twenty days; after which it is run off into strong casks, which are cooled in a cellar, and then sent into the market.

Oil of almonds, is manufactured by agitating the kernels in bags, so as to separate their brown skins, grinding them in a mill, then enclosing them in bags, and squeezing them strongly between a series of cast iron plates, in a hydraulic press; without heat at first, and then between heated plates. The first oil is the purest, and least apt to become rancid. It should be refined by filtering through porous paper. Next to olive oil, this species is the most easy to saponify. Bitter almonds being cheaper than the sweet, are used in preference for obtaining this oil, and they afford an article equally bland, wholesome, and inodorous. But a strongly scented oil may be procured, according to M. Planché, by macerating the almonds in hot water, so as to blanch them,then drying them in a stove, and afterwards subjecting them to pressure. The volatile oil of almonds is obtained by distilling the marc or bitter almond cake, along with water. SeePress, Hydraulic, andStearine.

Linseed, rapeseed, poppyseed, and other oleiferous seeds were formerly treated for the extraction of their oil, by pounding in hard wooden mortars with pestles shod with iron, set in motion by cams driven by a shaft turned with horse or water power, then the triturated seed was put into woollen bags which were wrapped up in hair-cloths, and squeezed between upright wedges in press-boxes by the impulsion of vertical rams driven also by a cam mechanism. In the best mills upon the old construction, the cakes obtained by this first wedge pressure, were thrown upon the bed of an edge-mill, ground anew, and subjected to a second pressure, aided by heat now, as in the first case. These mortars and press-boxes constitute what are called Dutch mills. They are still in very general use both in this country and on the Continent; and are by many persons supposed to be preferable to the hydraulic presses.

Roller-mill

The roller-mill, for merely bruising the linseed, &c., previous to grinding it under edge-stones, and to heating and crushing it in a Dutch or a hydraulic oil-mill, is represented infigs.770.and771.The iron shafta, has a winch at each end, with a heavy fly-wheel upon the one of them, when the machine is to be worked by hand. Upon the opposite end is a pulley, with an endless cord which passes round a pulley on the end of the fluted rollerb, and thereby drives it. This fluted rollerb, lies across the hopperc, and by its agitation causes the seeds to descend equably through the hopper, between the crushing rollersd,e. Upon the shafta, there is also a pinion which works into two toothed wheels on the shafts of the crushing cylindersdande, thus communicating to these cylinders motion in opposite directions.f,gare two scraper-blades, which by means of the two weightsh,h, hanging upon levers, are pressed against the surfaces of the cylinders, and remove any seed-cake from them. The bruised seeds fall through the slitiof the case, and are received into a chest which stands upon the boardk.

Machines of this kind are now usually driven by power. Hydraulic presses have been of late years introduced into many seed-oil mills in this country; but it is still a matter of dispute whether they, or the old Dutch oil-mill, with bags of seed compressed between wedges, driven by cam-stamps, be the preferable; that is, afford the largest product of oil with the same expenditure of capital and power. For figures of hydraulic presses, seePress, andStearine.

This bruising of the seed is merely a preparation for its proper grinding under a pair of heavy edge-stones, of granite, from 5 to 7 feet in diameter; because unbruised seed is apt to slide away before the vertical rolling wheel, and thus escape trituration. The edge-mill, for grinding seeds, is quite analogous to the gunpowder-mill represented infig.531.,page 630. Some hoop the stones with an iron rim, but others prefer, and I think justly, the rough surface of granite, and dress it from time to time with hammers, as it becomes irregular. These stones make from 30 to 36 revolutions upon their horizontal bed of masonry or iron in a minute. The centre of the bed, where it is perforated for the passage of the strong vertical shaft which turns the stones, is enclosed by a circular box of cast iron, firmly bolted to the bed-stone, and furnished with a cover. This box serves to prevent any seeds or powder getting into the step or socket, and obstructing the movement. The circumference of the mill-bed is formed of an upright rim of oak-plank, bound with iron. There is a rectangular notch left in the edge of the bed, and corresponding part of the rim, which is usually closed with a slide-plate, and is opened only at the end of the operation, to let the pasty seed-cake be turned out bythe oblique arm of the bottom scraper. The two parallel stones, which are set near each other, and travel round their circular path upon the bed, grind the seeds not merely by their weight, of three tons each, but also by a rubbing motion, or attrition; because their periphery being not conical, but cylindrical, by its rolling upon a plane surface, must at every instant turn round with friction upon their resting points. Strong cast-iron boxes are bolted upon the centres of the stones, which by means of screw clamps seize firmly the horizontal iron shafts that traverse and drive them, by passing into a slit-groove in the vertical turning shaft. This groove is lined with strong plates of steel, which wear rapidly by the friction, and need to be frequently renewed.

The seeds which have been burst between the rolls, or in the mortars of the Dutch mills, are to be spread as equably as possible by a shovel upon the circular path of the edge-stones, and in about half an hour the charge will be sufficiently ground into a paste. This should be put directly into the press, when fine cold-drawn oil is wanted. But in general the paste is heated before being subjected to the pressure. The pressed cake is again thrown under the edge-stones, and, after being ground the second time, should be exposed to a heat of 212° Fahr., in a proper pan, called a steam-kettle, before being subjected to the second and final pressure in the woollen bags and hair-cloths.

Steam-kettle and seed-stirrers

Fig.772.is a vertical section of the steam-kettle of Hallette, andfig.773.is a view of the seed-stirrer.a, is the wall of masonry, upon which, and the iron pillarsb, the pan is supported. It is enclosed in a jacket, for admitting steam into the intermediate spaced,d,d, at its sides and bottom.c, is the middle of the pan in which the shaft of the stirrer is planted upright, resting by its lower end in the stepe;f, is an opening, by which the contents of the pan may be emptied;g, is an orifice into which the mouth of the hair or worsted bag is inserted, in order to receive the heated seed, when it is turned out by the rotation of the stirrer and the withdrawal of the plugffrom the discharge aperture;h, is the steam induction pipe; andt, the eduction pipe, which serves also to run off the condensed water.

The hydraulic oil-press is generally double; that is, it has two vertical rams placed parallel to each other, so that while one side is under pressure, the other side is being discharged. The bags of heated seed-paste or meal are put into cast-iron cases, which are piled over each other to the number of 6 or 8, upon the press sill, and subjected to a force of 300 or 400 tons, by pumps worked with a steam engine. The first pump has usually 2 or 21⁄2inches diameter for a ram of 10 inches, and the second pump one inch. Each side of the press, in a well-going establishment, should work 38 pounds of seed-flour every 5 minutes. Such a press will do 70 quarters of linseed in the days’ work of one week, with the labour of one man at 20s.and three boys at 5s.each; and will require a 12-horse power to work it well, along with the rolls and the edge-stones.

I am indebted to my excellent friend Mr. E. Woolsey, for the following most valuable notes, taken by him at sundry mills for pressing oil; and remarks upon the subject of seed-crushing in general.

“The chief point of difference depends upon the quality of seed employed. Heavy seed will yield most oil, and seed ripened under a hot sun, and where the flax is not gathered too green, is the best. The weight of linseed varies from 48 to 52 lbs. per imperial bushel; probably a very fair average is 49 lbs., or 392 lbs. per imperial quarter. I inspected one of the seed-crusher’s books, and the average of 15 trials of a quarter each of different seeds in the season averaged 141⁄2galls. of 71⁄2lbs. each; say, 109 lbs. of oil per quarter. This crusher, who uses only the hydraulic press, and one pressing, informed me that

“The average of the seed he has worked, which he represents to be of an inferior quality, for the sake of its cheapness, yields 141⁄2galls. per quarter. I had some American seed which weighed 521⁄4lbs. per imperial bushel, ground and pressed under my own observation, and it gave me 111 lbs. oil; that is to say, 418 lbs. of seed gave 111 lbs. oil = 2656⁄100per cent. A friend of mine, who is a London crusher, told me the oil varied according to the seed from 14 to 17 galls.; and when you consider the relative value of seeds, and remember thatoilandcakefrom any kind of seed is of thesame value, it will be apparent that the yield is very different; for example,

The difference of 4s.must be paid for in the quantity of oil which at 38s.6d.per cwt. (the then price) requires about 111⁄2lbs. more oil expressed to pay for the difference in the market value of the seed. Another London crusher informed me that East India linseed will produce 17 gallons, and he seemed to think that that was the extreme quantity that could be expressed fromany seed. The average of last year’s Russian seed would be about 14 galls.; Sicilian seed 16 galls.

“Rape-seed.—I have not turned my attention to quantity of oil extracted from this seed; but a French crusher (M. Geremboret), on whom I think one may place considerable dependence, told me, that

“Rape-seed weighs from 52 to 56 lbs. per imperial bushel.”

The following are the heads of a reference of machinery for a seed oil-mill:—

1. Two pairs of cast-iron rollers, 19 inches long, and 10 inches in diameter, fixed in a cast-iron frame, with brasses, wheels, shafts, bolts, scrapers, hoppers, shoes, &c.

2. Two pairs of edge-stones, 7 feet diameter each, with two bottom stones, 6 feet diameter each, cast-iron upright shafts, sweepers, wheels, shafts, chairs, brasses, bolts, and scrapers, with driving spur-wheels, &c.

3. Five steam kettles, with wheels, shafts, and brasses, bolts, breeches, and steam pipes, an upright cast-iron shaft, with chairs and brasses at each end; and a large bevel wheel upon the bottom end of upright shaft, and another, smaller, upon fly-wheel shaft, for the first motions.

4. Five stamper presses, with press plates of cast iron, cast-iron stamper shaft with 10 arms and 10 rollers, with bosses, brasses, bolts, driving bevel-wheels.

A well made oil-mill, consisting of the above specified parts, will manufacture 200 quarters of seed per week.

I have been assured by practical engineers, conversant in oil-mills, that a double hydraulic press, with 2 ten-inch rams, will do the work of no more than two of the stamper presses; that is to say, it will work 22 quarters in 24 hours; while three stamper presses will work 33 quarters in the same time, and produce one half more oil.

Castor oil, quantity of,

Duty, from British possessions, 2s.6d.per cwt.; from foreign, 1s.per lb.

Cocoa-nut oil, quantity of,

Olive oil, quantity of,

Duties on olive oil, not of Naples and Sicily, 4d.; of Naples and Sicily, 8d.; and, if in ships of these countries, 10d.per gallon.

Train oil, spermaceti, and blubber, quantity of,

Duties on oil taken by British ships, 1s.; by foreign fishers,£26 18s.per tun.

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