oils

oils term commonly used to indicate a variety of greasy, fluid substances that are, in general, viscous liquids at ordinary temperatures, less dense than water, insoluble in water but soluble in alcohol and ether, and flammable. These substances, however, differ so much among themselves in chemical composition that, in chemistry, their classification in one group is not practical and is employed only in a general way in accordance with popular usage. Petroleum and substances obtained from it, which are mixtures of hydrocarbons , are classed together, because of their origin, as mineral oils. They are widely used as fuels, illuminants, and lubricants. Distinguished from these in that they are obtained from animals and plants and are mixtures of carbon-hydrogen-oxygen compounds are the fatty oils or fixed oils. There is fundamentally no difference between fatty oils and fats (see fats and oils ). Such oils are used extensively as lubricants and in the making of soap . Depending upon their ability to oxidize when exposed to the atmosphere and form a thin, skinlike layer over substances upon which they are spread, the fixed, or fatty, oils are classed as drying or nondrying oils. The drying oils, e.g., linseed, hempseed, and poppy seed oil, are used in making paints and varnishes. On the other hand, such vegetable oils as olive, rapeseed, and castor oil and such animal oils as lard oil and neat's-foot oil do not possess this property and fall into the nondrying group. Another large and varied group of oils is recognized, the essential oils or volatile oils, which occur in plants but differ from the fixed, or fatty, oils in that they are volatile. In general, they give to the plant in which they are found its characteristic odor, flavor, or other properties peculiar to it.

oil General term to describe a variety of substances whose chief shared properties are viscosity at ordinary temperatures, a density less than that of water, inflammability, insolubility in water, and solubility in ether and alcohol. Mineral oils, most notably crude oil or petroleum oil, are used as fuels. Animal and vegetable oils (fatty oils or fats) are used as food, lubricants and as a major ingredient of soap. In addition, there are essential oils from plants that, unlike fatty oils, are volatile. Fatty oils can be classified into two groups: drying, such as linseed and poppyseed oil, and non-drying, such as olive and castor oil.

oil Any of various viscous liquids that are generally immiscible with water. Natural plant and animal oils are either volatile mixtures of terpenes and simple esters (e.g. essential oils) or are glycerides of fatty acids.