A dispersion of droplets of one liquid in another immiscible liquid. Its interfacial energy and kinetic persistence depend on droplet size, interfacial tension and stabilizing species.
Merging of droplets after their separating film fails. This differs from clustering of still-distinct droplets. Interfacial protection can delay merging without making the two bulk liquid phases molecularly miscible.
A surfactant-stabilized dispersion can remain macroscopically uniform while its two liquids remain distinct phases. Lower interfacial tension reduces the work of making droplets, and repulsive interfacial films can slow droplet coalescence. Kinetic emulsion stability does not by itself establish equilibrium molecular miscibility or a thermodynamically stable microemulsion.
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An emulsion is a mixture of two immiscible liquids, typically oil and water, in which one liquid is dispersed in the form of tiny droplets throughout the other. Emulsions are unstable by nature, as the two liquids do not mix well. To achieve stability and prevent the droplets from coalescing, emulsifiers or stabilizers are often added. These are substances that have dual affinity, meaning they can interact with both the oil and water phases.