OIL-BEETLE 



OILS 



587 



through impaired nutrition, the young shoots fall 

 victims, and lastly the grapes. Powdered sulphur 

 was found useful as a cure, but the applications 

 had to be very frequent ; in consequence of its 

 importance the duty of sulphur was reduced by the 

 French government. It is probable that in this 

 case, as in all diseases of the sort, the general 

 vitality of the organism must be lowered before it 

 will fall a victim. Over-cultivation and long use 

 of the same ground are predisposing causes. 



Oil-beetle, a name given to beetles of the 

 Melee and allied genera, which when disturbed 

 emit a yellowish oily liquor from the joints of their 

 legs. Some species are used as vesicants instead 

 of cantharides. 



Oil-bird. See GUACHARO. 



Oil-cake is used mainly for feeding sheep and 

 cattle. It is made from the solid residne of oleagin- 

 ous seeds ( linseed, rape-seed, cotton-seed ), after a 

 large proportion of their oil has been extracted. 

 The following is the usual process of manufacture 

 in Britain. The seed is crushed between iron 

 rollers, then damped and ground upon a mill of 

 the following construction. Two large circular 

 blocks of hard granite are set edgewise on a bed- 

 Rtone of the same material, which is slightly 

 hollowed out; these two upright stones are con- 

 nected by a horizontal shaft which passes through 

 the centre of both, and is fixed at its middle to a 

 revolving upright shaft. The stones are thus made 

 to revolve about their vertical axes, while at the 

 same time they are left free to be turned round the 

 horizontal shaft by the friction of grinding. The 

 meal thus obtained is heated in kettles formed of 

 two compartments, in the inner of which the meal 

 is placed, while the outer is filled with steam. The 

 meal is then filled into small woollen bags of the 

 shape it is wished to make the cakes usually 

 oblong, about :v> inches by 12 incites, and * to f 

 inch thick. These bags are then placed in wooden 

 ' wrappers,' which consist of two pieces of hard 

 wood, of the same size as the cakes, hinged to- 

 gether at the end ; the wood is usually corrugated 

 and furnished with a stamp to mark the cakes. 

 The wrapirs containing the bags full of crushed 

 seed are then placed in the compartments of a 

 press worked on the same principle as a Hydraulic 

 Press (q.v.), except that the oil from the seed is 

 used instead of water. In this way about 90 per 

 cent, of the oil the seed contaitis is squeezed out 

 of it, leaving sufficient to bind the residue of 

 ground husks into a solid firm cake. Sometimes 

 the process is varied, in that the seed, instead of 

 being ground under stones, is repeatedly crushed 

 on iron rollers ; in this case the crushed seed is 

 steamed in the kettles to give the necessary 

 moisture, not merely heated as described al>ove. 

 Sometimes oil-seeds are subjected to a chemical 

 instead of a mechanical process viz. solution of 

 the oil in bisulphide of carton. By this means the 

 oil may be almost completely extracted. Mustard, 

 rape, castor-oil, undecorticated cotton-seed cake, 

 and some others are also used as fertilisers. 



Oil City, Pennsylvania, on both sides of the 

 Alleghany River (here crossed by long railroad 

 and passenger bridges), 133 miles by rail N. by E. 

 of Pittsburgh, is one of tlie principal oil markets in 

 the state, and the centre of a busy trade. It con- 

 tains, besides oil-refineries, engine- and Inriler- 

 factories, and a large cooperage. There were fearful 

 inundations here in June 1892. Pop. (1870) 2276; 

 (1880)7315; (1900)13,264. 



Oil-fuel, Oil-lias. See FUEL, GAS-LIGHTINQ, 

 PETROLEUM. For Oil-engine, see GAS ENGINE. 



Oil Palm. See OILS, and PALM. 

 Oil Rivers. See NIGER. 



Oils (including Fats). The fats and fixed oils 

 constitute an important and well-marked group of 

 organic compounds, which exist abundantly both 

 in the animal and vegetable kingdoms. They are 

 not simple organic compounds, but each of them is 

 a mixture of several such compounds to which the 

 term f/lifcerides is applied ; and the glycerides which 

 by their mixture in various proportions form the 

 numerous fats and oils are mainly those of palmitic, 

 stearic, and oleic acids, and to a less extent those 

 of other fatty acids, such as butyric, canroic, cap- 

 rylic, and capric acids, which are obtained from 

 butter, myristic acid, which is obtained from cocoa- 

 nut oil, &c. The members of this group may be 

 solid and hard, like suet ; semi-solid and soft, like 

 butter, horse-grease, and lard; or fluid, like the 

 oils. The solid and semi-solid are, however, 

 usually placed together and termed fats, in con- 

 tradistinction to the fluid oils. The most solid 

 fats are readily fusible, and become reduced to a 

 fluid or oily state at a temperature lower than 

 that of the boiling-point of water. It is not until 

 a temperature of between 500 and 600 F. is reached 

 that they begin nearly simultaneously to boil and 

 to undergo decomposition, giving off acroleine (an 

 acrid product of the distillation of glycerine) and 

 other compounds. In consequence of this property 

 these oils are termed fixed oils, in contradistinction 

 to a perfectly separate group of oily matters, on 

 which the odoriferous properties of plants depend, 

 and which, from their being able to bear distilla- 

 tion without change, are known as volatile oils. 

 These, which are also known as essential oils, differ 

 lit toto in their chemical coinposition from the com- 

 pounds we are now considering. All the fats and 

 oils are lighter than water, and are perfectly in- 

 soluble in that fluid. Their specific gravity ranges 

 from about 0-91 to 0'94. They dissolve in ether, 

 oil of turpentine (one of the volatile oils), benzol, 

 and to a certain extent in alcohol ; while, on the 

 other hand, they act as solvents for sulphur, phos- 

 phorus, &c. These bodies possess the property 

 of penetrating paper and other fabrics, rendering 

 them transparent, and producing what is well 

 known as a greasy stain. They are not readily 

 inflammable unless with the agency of a wick, 

 when they burn with a brijjht flame. In a pure 

 ami fresh state they are devoid of taste and smell, 

 but on exposure to the air they become oxidised 

 and acid, assume a deeper colour, evolve a dis- 

 agreeable odour, and are acrid to the taste; or, 

 in popular language, they become rancid. The 

 rapidity with which this change occurs is consider- 

 ably increased by the presence of mucilaginous or 

 albuminous liodies. The rancidity may be removed 

 by shaking the oil in hot water in which a little 

 hydrated magnesia is suspended. 



The general diffusion of fats and oils in the 

 animal kingdom has been already described (see 

 FATS). In the vegetable kingdom they are 

 equally widely distributed, there being scarcely 

 any tissue of any plant in which traces of them 

 may not be detected ; but they are specially 

 abundant in the seeds. The seeds of the Cruciferas 

 are remarkably rich in oil ; linseed yielding fully 

 20 per cent., and rape-seed about 40 per cent, of 

 oil ; and some fruits, as those of the olive and oil- 

 palm, yield an abundance of oil. 



The uses of oils and fats are numerous and 

 highly important, many being extensively em- 

 ployed as articles of food, as medicines, as lubri- 

 cating agents, in the preparation of soaps, oint- 

 ments, varnishes, pigments, for candles, lamps, and 

 other means of illumination, and for the purpose 

 of dressing leather, &c. In Africa, Asia, and the 

 Pacific animal and vegetable oils and fats are 

 much used for anointing the person and smearing 

 the hair, thus affording a protection aga.nst heat 



