Any greasy substance liquid at room temperature and insoluble in water. It may be a fixed (nonvolatile) oil, an essential oil, or a mineral oil (see petroleum). Fixed oils and fats (derived from animals and plants) have the same chemical composition—both are esters of glycerol and fatty acids. These oils have a variety of industrial and food uses. Linseed, tung, and other drying oils are highly unsaturated (see saturation); these and large quantities of soybean, sunflower, and safflower oils (also constituents of foods) are used in paints and varnishes. When exposed to air they absorb oxygen and polymerize (see polymerization), forming a tough coating. Some specialty oils and oil derivatives are also used in leather dressing and textile manufacture.

This entry comes from Encyclopædia Britannica Concise.
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