Solubilization resembles emulsification in regard to how they are caused by surfactant self-assemblies. Here, the distinct difference is that solubilization is a state under thermodynamic equilibrium and thus is independent to the process applied, but on the other hand, emulsion is an unstable non-equilibrium state highly dependent on the preparation process. Systems called microemulsions require special attention because despite of the name, they are states in solubilization where swelled micelles are dispersed. The term solubilization is generally used for isotropic single-phase micelle solutions higher than the Kraft temperature, though there are recent trends to include lyotropic liquid crystals and gels.
The maximum solubilization by micelles for slightly soluble substances at certain temperature is quite important to measure. Therefore, this chapter deals with solubilization of volatile and/or nonvolatile substances by surfactant micellar solution.