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 le ferruginous, and are accompanied by gray plastic clays, of a yellowish or reddish colour; all of them substances which contribute more or le 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 ma ive; 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 Shot over 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 | 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 ma ive, 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 cla es: the fat or fixed oils, huiles gra es , Fr.; Fette oele , Germ.; and the e ential or volatile oils , Huiles volatiles , Fr.; Flüchtige , aether is che 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 cla , is not so correct, since some of them are obtained by expre ion, as the whole of the first cla 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 po e 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, a ociated with mucilage, especially in those of the bicotyledinous cla , 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, ., or mixed in a liquid state with other animal matters, as in the milk. Bra con not, but particularly Raspail, have shown that animal fats consist of small microscopic, partly polygonal, and partly reniform particles, a ociated by means of their containing sacs. These may be separated from each other by tearing the recent fat asunder, rinsing it with water, and pa ing 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 pre ure. These are lighter than water, but sink readily in spirit of wine. When boiled in strong alcohol, the oily principle di olves, 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: | No. | Plants. | Oils. | Spe- cific gravity. | | 1. | Linum us it at is sum et perenne | D. | Linseed oil | 0 | ·9347 | | 2. | Coryleus avellan a | | - | D. | Nut oil | 0 | ·9260 | | 3. | Juglans regia | | 4. | Papaver somniferum | D. | Poppy oil | 0 | ·9243 | | 5. | Cannabis sativa | D. | Hemp oil | 0 | ·9276 | | 6. | Sesamum orientale | G. | Oil of sesamum | | | 7. | Olea Europe a | G. | Olive oil | 0 | ·9176 | | 8. | Amygdal us communis | G. | Almond oil | 0 | ·9180 | | 9. | Gui land in a mohringa | G. | Oil of behen or ben | | | 10. | Cucurbit a pepo, and melapepo | D. | Cucumber oil | 0 | ·9231 | | 11. | Fagus silvatic a | 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. | Bra ica nap us et campestris | G. | Rape seed oil | 0 | ·9136 | | 15. | Ricinus communis | D. | Castor oil | 0 | ·9611 | | 16. | Nicotiana tabacum et rustic a | D. | Tobacco seed oil | 0 | ·9232 | | 17. | Prunus domestic a | G. | Plum kernel oil | 0 | ·9127 | | 18. | Vitis vinifera | D. | Grape seed oil | 0 | ·9202 | | 19. | Theobroma cacao | G. | Butter of cacao | 0 | ·892 | | 20. | Cocos nucifera | G. | Cocoa nut oil | | | 21. | Cocus butyracea vel avoira elais | G. | Palm oil | 0 | ·968 | | 22. | Laurus nobilis | G. | Laurel oil | | | 23. | Arachis hypogæa | G. | Ground-nut oil | | | 24. | Vateria indica | G. | Piney tallow | 0 | ·926 | | 25. | Hesperis matronal is | D. | Oil of Julienne | 0 | ·9281 | | 26. | Myagrum sativa | D. | Oil of camel in a | 0 | ·9252 | | 27. | Reseda luteola | D. | Oil of weld-seed | 0 | ·9358 | | 28. | Lepidium sativum | D. | Oil of garden cre es | 0 | ·9240 | | 29. | Atropa belladonna | D. | Oil of deadly nightshade | 0 | ·9250 | | 30. | Go ypium Barb a dense | D. | Cotton seed oil | | | 31. | Bra ica campestris oleifera | G. | Colza oil | 0 | ·9136 | | 32. | Bra ica 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 | | 35. | Pyrus mal us | G. | Apple seed oil | | | 36. | Euonymus Europæus | G. | Spindle tree oil | 0 | ·9380 | | 37. | Cornus sanguine a | G. | Cornil berry tree oil | | | 38. | Cyperus esculent a | G. | Oil of the roots of cyper gra | 0 | ·9180 | | 39. | Hyosciamus niger | G. | Henbane seed oil | 0 | ·9130 | | 40. | Æscul us 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 esculent a , 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 bra ica 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 expre ed 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 progre 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 pre ure 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 undi olved. 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 proce succeeds only with recently expre ed 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 ve els, oils may be preserved fresh for a very long time, but with contact of air they undergo progre ive 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 le combustible, and a ume 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. Sau ure 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 progre ively, 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 ma , 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, mo , 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 di olves 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, a ume 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 di olves in small quantity in the oils, and so does verdigris. The latter solution is green. Oils di olve also several of the vegetable alkalis, as morphia, cinch on i a, 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 | Sau ure. | | Oleine of oliv 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 Sau ure concludes that the le fusible fats contain more carbon and le 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 expre ed oils. Oil of almonds , according to Gu eron, contains no stearine; at least he could obtain none by cooling it and squeezing it succe ively till it all congealed. Bra con not had, on the contrary, said, that it contains 24 per cent. of stearine. I believe that Gu eron is right, and that Bra con not had made fallacious experiments on an impure oil. Oil of colza , is obtained from the seeds of bra ica 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 avellan a 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 pre ure; 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 pre ure, he obtains from 26 to 27. In the Encyclopædia Metropolitan a, under Oil Pre , 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 impo ible quantity. Such are the errors introduced into respectable books, by adopting without practical knowledge, the puffing statements of a patentee. It di olves 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 ma es of white stearine along with a brownish powder. That stearine is very difficult of saponification.