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see colloidcolloid
[Gr.,=gluelike], a mixture in which one substance is divided into minute particles (called colloidal particles) and dispersed throughout a second substance. The mixture is also called a colloidal system, colloidal solution, or colloidal dispersion.
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a disperse system consisting of droplets of a liquid (the dispersed phase) distributed evenly throughout another liquid (the dispersion medium).

A distinction is made between emulsions of the oil-in-water type (with droplets of a nonpolar liquid, such as a mineral oil, dispersed in a polar medium, usually water) and reverse emulsions of the water-in-oil type (with droplets of a polar liquid in a non-polar medium). Multiple emulsions are also encountered, in which the droplets of the dispersed phase serve as the dispersion medium for even finer droplets of another dispersed phase.

Emulsions are also divided into lyophilic and lyophobic types (seeLYOPHILIC AND LYOPHOBIC COLLOIDS). Lyophilic emulsions are thermodynamically stable, reversible systems that are formed spontaneously at temperatures close to the critical displacement temperature for two interacting liquids. Lyophobic emulsions are thermodynamically unstable systems formed by the mechanical, acoustic, or electrical dispersion of one liquid in another or by the separation of droplets from a supersaturated solution or melt; such emulsions may exist for prolonged periods only if mixed with an emulsifier. Lyophilic emulsions are highly dispersed (colloidal) systems, the droplets of which measure no more than 10–5 cm. Lyophobic emulsions are coarsely (poorly) dispersed systems with droplet size usually ranging from 10–5 to 10–2 cm. If the dispersed phase and dispersion medium differ greatly in density, the emulsion will be kinetically unstable—that is, the particles of the dispersed phase will tend either to sink to the bottom or rise to the top. The sedimentation of emulsion droplets that are well protected against coalescence may lead to the concentration of the droplets and the formation of creams or sediments of continuous two-liquid phases not separated into discrete layers.

The type and properties of an emulsion depend on such factors as its composition, the relative proportions of the liquid phases, the quantity and chemical nature of the emulsifier, the method of emulsification, and the temperature at which the emulsification is carried out. A change in the composition of an emulsion or in the action of the emulsifier may produce a phase inversion, in which an oil-in-water emulsion becomes a water-in-oil emulsion or vice versa.

Dilute emulsions are typical liquids, with droplets that move freely and independently of one another in a highly mobile medium. In emulsions with droplets of uniform size, as the concentration of the dispersed phase exceeds 74 percent by volume, the viscosity of the system increases abruptly, and the emulsion becomes a gel. In the process, droplets that initially had a spherical shape are highly deformed in such a way that they come to resemble polyhedrons. The content of the dispersed phase in highly concentrated emulsions may be as high as 99 percent by volume; in such cases, the dispersion medium is retained between the droplets in the form of fine layers that resemble the liquid films between bubbles in foams.

Emulsions with various compositions and properties are commonly used in industry, agriculture, and medicine; they also have household uses. Many foods, such as milk and egg yolks, are multicomponent emulsions, as are unrefined petroleum and the milky juices of plants.

Among the products that take the form of emulsions are cooling lubricants and various pesticides, cosmetics, drugs, and binders for latex paints. Asphalt emulsions are used in construction.


Voiutskii, S. S. Kurs kolloidnoi khimii, 2nd ed. Moscow, 1975. Pages 367–81.
Emul’sii. Leningrad, 1972. (Translated from English.)
Becher, P. Emulsions: Theory and Practice, 2nd ed. New York, 1965.
Emulsions and Emulsion Technology, parts 1–2. Edited by K. J. Lissant. New York, 1974.



A stable dispersion of one liquid in a second immiscible liquid, such as milk (oil dispersed in water).
(graphic arts)
In photography, the photosensitized material on film, plates, and various photographic papers.


1. A mixture of liquids insoluble in one another, in which one is suspended in the other in the form of minute globules.
2. A mixture in which solid particles are suspended in a liquid in which they are insoluble, as a mixture of bitumen and water, with uniform dispersion of the bitumen globules. The cementing action needed in roofing and waterproofing takes place as the water evaporates.


emulsionclick for a larger image
A suspension of a light-sensitive silver salt, especially silver chloride or silver bromide in a colloidal medium—usually gelatin—which is used for coating photographic films, plates, and paper.


1. Photog a light-sensitive coating on a base, such as paper or film, consisting of fine grains of silver bromide suspended in gelatine
2. Chem a colloid in which both phases are liquids
3. a type of paint in which the pigment is suspended in a vehicle, usually a synthetic resin, that is dispersed in water as an emulsion. It usually gives a mat finish
4. Pharmacol a mixture in which an oily medicine is dispersed in another liquid
References in periodicals archive ?
The oil-in-water emulsion composition is comprised of an emollient; a surfactant selected from the group consisting of nonionic surfactants, amphoteric surfactants, anionic surfactants, cationic surfactants and combinations thereof; a preservative, wherein said preservative is a paraben-based antimicrobial comprising methylparaben, ethylparaben and propylparaben; at least 0.
Using a laboratory instrument called an infrared spectrometer (IR spectrometer) they verified that sausages made with heart-healthy olive oil-in-water emulsion stabilized with casein were slightly tougher.
Fletcher, "Retardation of Oil Drop Evaporation from Oil-in-Water Emulsions," Chem.
Multilayer oil-in-water emulsion systems can be used to design interfacial layers needed for a required function.
The process has the following steps: mixing a polymer compound that has, in a side chain, a group represented by the formula -(OX)n-E2-R, wherein X represents a C1 to C6 linear or branched divalent saturated hydrocarbon group, n is a number of 5 to 300, Xs whose number is n may be the same as or different from one another, E2 represents an ether linkage (--O--) or an ester linkage (--OCO--or--COO--), and R represents a C4 to C30 linear or branched hydrocarbon group which may be substituted with a hydroxy group; a water-soluble polyol; a nonionic surfactant; a hydrophobic compound and water; then diluting the resulting mixture with water, so that the average emulsion particle diameter of the emulsion in the oil-in-water emulsion is 0.
In essence, this involves submicron oil-in-water emulsion creams, which facilitate a drug's penetration into the skin.
The technology is based on a natural oil-in-water emulsion derived from plant oil seeds.
A stock oil-in-water emulsion was prepared by homogenizing olive oil with 10mM SDS/8mM Tween 20 surfactant solution that had been adjusted to pH 3 using hydrogen chloride (HCl).
Midland, MI, patented a method to make an aqueous silicone resin containing emulsion by mixing a silicone resin blend, a non-resinous silicone polymer and an inversion assisting polymer to form a homogeneous oil phase; mixing one or more surfactants with the homogenous oil phase; adding water to the mixture to cause an inversion of the continuous phase and the dispersed phase, forming an oil-in-water emulsion; diluting the oil-in-water emulsion by adding more water and recovering an oil-in-water emulsion with silicone particles ranging 0.
Many oil-in-water emulsions contain chelators that can alter lipid oxidation rates.
Surface active proteins have been used as emulsifiers not only to form physically stable emulsions, but also to increase the oxidative stability of oil-in-water emulsions.