https://doi.org/10.1351/goldbook.14317
Dispersion made of water, oil, and surfactant(s) that is an isotropic and thermodynamically stable system with dispersed domain diameter varying approximately from \(\pu{1 nm}\) to \(\pu{100 nm}\), usually \(\pu{10 nm}\) to \(\pu{50 nm}\).
Notes:
- In a micro-emulsion the domains of the dispersed phase are either globular or interconnected (to give a bicontinuous micro-emulsion).
- The average diameter of droplets in macro-emulsion (usually referred to as an "emulsion") is close to one millimeter (i.e., \(\pu{E-3 m}\)). Therefore, since micro- means \(\pu{E-6 m}\) and emulsion implies that droplets of the dispersed phase have diameters close to \(\pu{E-3 m}\), the micro-emulsion denotes a system with the size range of the dispersed phase in the \(\pu{E-6} \times \pu{E-3 m} = \pu{E-9 m}\) range.
- The term "micro-emulsion" has come to take on special meaning. Entities of the dispersed phase are usually stabilized by surfactant and/or surfactant-cosurfactant (e.g., aliphatic alcohol) systems.
- The term "oil" refers to any water-insoluble liquid.