Page:The New International Encyclopædia 1st ed. v. 14.djvu/899

* OILCLOTH. 767 OILS. figure are then cut away. See History and Manu- fucliire o[ Floar Voccring (New York, 1899). OIL-FISH, or Golomyxka. A remarkable iisli (Coincpliorus Baiktilcnsis) of the blcuuy family, living only in Lake Baikal (q.v.). It 13 alniiit a foot long, is destitute of scales, and is very soft, its whole substance abounding in oil, which is obtained from it by pressure. It is never eaten. In winter it retires to great depths, but in summer approaches the shores, and great numbt'rs often are stranded. OILLET (OF., eyelet), or (Kii.i.et. A small opening or window, often circular, used in me- diieval buildings; also called (X'il de boeuf. OIL PALM (Elcris). A genus of palms of the same tribe with the cocoanut palm. The best known species, Eheis yuinecnsis, sometimes at- tains a height of 20 to 30 feet, has pinnate leaves with spiny footstalks and flowers with an odor like anise or chervil. The fruit forms an immense head, like a great pineapple, consisting of a large number of bright orange-eolorod thin- skinned drupes, with hard stones and oily pulps, which by bruising and boiling yield a bland violet-smelling oil which when taken to cold climates becomes butter-like in consistency. This oil, now largely exported from tropical Africa, is much used for making candles, toilet soaps, etc., but when fresh is catdn like butter. The nut Avas formerly rejected as useless after the oil had been obtained from the fruit; but from its kernel a fixed clear and limpid oil called palm-nut oil is extracted and has become to some ex-tent an article of commerce. OIL RIVEES. A name applied to the chan- nels lurming the delta of the Niger (q.v.) in ^■est Africa and the neighboring small independ- ent rivers, on account of the vast forests of oil palms which line their banks (ilap: Africa, E 4). The surrounding district, a British de- ])endency, was formerly known as the Oil Eivers Protectorate, but is now a part of Southern Nigeria. OILS (OF. olle, ole, idle, Fr. hidlc. from Lat. oleiiDi, oil, from Gk. eTiaiov, elaion, oil, olive oil, from e?.aiaj elaia, olive tree). A term applied to a large number of liquids characterized by being insoluble in water and being highly viscous. Their 'greasy feeling' often mentioned as an additional characteristic is due largely to their viscosity and insolubility in water. Capa- bility of saponification (see further below), for- merly considered essential, is confined to a variety of substances, chiefly of animal or vegetable origin, while the unsaponifiable class includes the so-called mineral oils and similar products pre- pared artificially. Chemically the oils possess no property in common w'hieh would justify their being grouped together in any rational classifica- tion of substances. And if they arc still referred to collectively as a distinct class of chemical substances, it is owing partly to custom, partly to the fact that chemically different oils are sometimes associated industrially. LiQilD Fats. The vegetable and aninial oils of liquid fats do not differ essentially from the class of sulistani-es described under Fat.s. They, too, contain olcin, palmitin, and stearin, to- gether with certain other fatty bodies, which give each oil its cliaracteristic properties. Palm- itin and stearin are solids at ordinary- tempera- ture, but are freely soluble in the liquid olein, and a liquid fat is essentially a solution in one proportion or another of palmitin and stearin in olein. Olive, cottonseed, corn, linseed, and lard oils are types of this class of oils, all of which are soluble in ether, carbon disulphide, chloroform, hydrocarbons, etc. All of the fatty oils are also capable of being saponified, i.e. of being broken up into glycerin and so-called fatty acids. The term '.saponifica- tion' (from Lat. sapu, soap) is used on account of the decomposition being oftenest eH'ccted by the use of caustic soda or potash, which combines with the freed fatty acids to form the mixtures of salts well known as soaps. There are, however, other methods by which the decomposition may be sometimes brought aboiit. And since, what- ever the method, the decomposition is accom- panied by the chemical absorption of the ele- ments of water, it is more exactly referred to, not as saponification, but as hydrolysis, or hydro- lytic splitting. The several methods by which the hydrolysis of oils may be brought about in- clude: (1) Boiling with caustic alkali; (2) the action of steam under high pressure; (3) bacterial action, e.g. when fats become rancid; (4) the action of dry heat. The following classification of these compounds by A. H. Allen will be found useful ; it serves to illustrate the origin and approximate compo- sition of the more common oils. Olive Oil Group, vegetable oleins, non-vola- tile, high viscosity, non-drying, insoluble in al- cohol. Rape Oil G-roup, derived from the Cruciferoe, non-volatile, highest viscosity, non-drying, in- soluble in alcohol. Cottonseed Oil Group, non-volatile, medium viscosity, semi-drying, insoluble in alcohol. Linseed Oil Group, drying oils, non-volatile, absorb oxygen, insoluble in alcohol, low viscosity. C'asitor Oil Group, distinctly dilVerent from the above in cljemical composition by reason of con- taining a large proportion of hydroxv-fatty acids including ricinoleic acid — highest viscosity, sol- uble in alcohol and glacial acetic acid, non-vola- tile, non-drying. Lard Oil Group, animal oleins, non-volatile, non-drying, high viscosity. Whale Oil Group, marine animal oils, slightly volatile, low viscosity, partly drying, darken with chlorine, characteristic odor. Palm and cocoanut oils are omitted because solid at ordinary temperatures. Sperm oil is not a true oil, but a liquid wax. Plants contain a greater variety and, as a rule, relatively larger quantities of oils than animals. Vegetable oils are obtained by the simple process of grinding or crushing and hy- draulic pressing of seeds or kernels, which con- tain the largest proportion of oil. At times the ground materials are pressed cold and hot, the cold process yielding better products, but smaller quantities. Of late years extraction processes using light hydrocarbon solvents are much used. The solvents are allowed to act on the crushed material at a slightly elevated temperature; on exhaustion, the liquid is drawn otT. and the sol- vent is separated by distillation. Oils produced by this process are very free from foots or gelatinous material, but. on the other hand, are liable to he contaminated with resins and color- ing matters or any other material soluble in