Solubility limits and phase diagrams for fatty acids in anionic (SLES) and zwitterionic (CAPB) micellar surfactant solutions

► Solubility limits of fatty acids in micellar surfactant solutions are determined. ► The solubility limits increase proportionally to the surfactant concentration. ► The mixing of the two components in the micelles can be both ideal and non-ideal. ► The interaction parameter depends on the chainlength mismatch. ► Phase diagrams of the investigated mixed solutions are obtained.