ODOMETER (See PARwxsULATOR). OIL. The term oil is applied to two dissimilar and distinct organic products, which are usually called Aced oils, and volatile oils. The fixed or fat oils are either of vegetable or animal origin ; they are compounds of carbon, hydrogen, and oxygen; the relative proportions vary but little in the several species. The fol lowing analyses of olive and spermaceti oil may be assumed as types of the rest: Olive Oil. Spermaceti Oil.
Carbon 772 780 Hydrogen 133 118 Oxygen 95 102 1000 10D0 The fixed oils abound in the fruit and seed of certain plants ; they are lighter than water, unctuous, and insipid, or nearly so : some of these require a low temperature for their congelation, ouches linseed oil ; others, such as olive oil, con crete at a temperature higher than the freezing point of water; some are solid at common temperature, such as coeoa-nut oil. Some of these oils when exposed to air absorb oxygen, and gradually harden, forming a kind of varnish ; these are called drying oils, and are the basis of paints, such as linseed oil; others be come rancid, as almond oil. All these oils, like the different kinds of fat, con sist of two proximate principles, called *Marine and elaine—the former is the fatty portion, which first concretes on cooling the oil, and from which the elaine, or oily portion, may be separated by pressure. These oils cannot be vola tilized without decomposition. At a red heat they are resolved into volatile and gaseous products, among which carbur etted hydrogen, in several of its forms predominates ; hence the use of these oils, when volatilized and burned by the aid of a wick, as sources of artificial light. The action a the alkali on the fat oils is Wieldy important, as forming soap.
The volatile ale are generally Obtained by distilling the vegetables, which afford them, with water ; they fluctuate in density a little on either side of water ; they are sparingly soluble in water, form ing the perfumed or medicated waters, such as rose and peppermint water ; they are mostly soluble in alcohol, forming essences. A few of them, such as oil of turpentine, of lemon peel, of copivi bal sam, cte., are hydrocarbons, that is, con sist of carbon and hydrogen only ; the greater number, however, contain oxy gen as one of their ultimate elements.
They are chiefly used in medicine and in perfumery, and a few of them are exten sively employed in the arts as vehicles for colors, and in the manufacture of var nishes ; this is especially the ease with oil of turpentine.
The fixed or fat oils are widely distri buted 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 dico tyledinons class, occasionally in the fleshy pulp surrounding some seeds, MI 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 mat ter occurs inclosed in thin membraneous cells, between the skin and the flesh, be tween the muscular fibres, within the ab dominal cavity in the omentum, upon the intestines, and round the kidneys, and in a bony receptacle of the scull of the spermaceti whale ; sometimes in special organs, as of the beaver ; in the gall bladder, itc., or mixed in a liquid state with other animal matters, as in the milk.
Braconnot, but particularly Respell, 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 re tained, the granular particles are observed to float in the water, and afterwards to separate, like the globules of starch, in a white pulverulent send-crystaline form. The particles consist of a strong mem braneous 'skin, inclosing steams and elaine, or solid and liquid fat, which may be extracted by trituration and pressure. These are lighter than water, but sink readily in spirits of wine. When boiled in strong alcohol, the oily principle dis solves, 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 diame ter; 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.