Emulsion

Emulsion, preparation of minute drops of one liquid dispersed evenly throughout another liquid. Each liquid is called a phase. One phase is usually water or an aqueous solution, and the other phase is usually an oil or other immiscible liquid. An emulsion consisting of oil droplets dispersed in water, called an oil-in-water emulsion, has properties like those of water, although an oil-in-water emulsion may contain so much oil that it is a semi-solid paste in consistency. If water droplets are dispersed in oil, the emulsion is a water-in-oil emulsion and has the properties of an oil. An emulsion is made by shaking or stirring the 2 liquids together, or beating them in a homogenizer. Unless the emulsion is very dilute, it requires an emulsifying agent such as a soap to prevent the dispersed droplets from coagulating together. Milk, butter, and mayonnaise are all emulsions. Emulsions are used in pharmaceutical preparations, cosmetics, paints, asphalt, and lubricants. The word emulsion is also used to describe the light-sensitive coating on a photographic film.