Emulsion

Article By:

Schramm, Laurier L. Saskatchewan Research Council, Saskatchewan, Canada.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.231100

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• Emulsion, published June 2014:Download PDF Get Adobe Acrobat Reader

A system of small liquid droplets dispersed in a second, immiscible liquid. Emulsions are a type of colloidal dispersion. By classical definition, emulsion droplets have diameters between 1 nanometer and 1 micrometer (see illustration). However, for practical purposes, the principles of colloid science can be usefully applied to emulsions whose droplets are as large as tens or even hundreds of micrometers. The droplets in an emulsion are large enough that they do not behave like the atoms and molecules of classical chemistry. For example, emulsions do not generally behave like true solutions and may have undetectable freezing-point depressions. On the other hand, the droplets are small enough that they do not behave like the macroscopic particles of classical physics. For example, emulsion droplets may rise (cream) or fall (sediment) extremely slowly in apparent violation of Stokes' law. See also: Colloid; Sedimentation (industry)

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