Studies on the Middle-phase Microemulsion of Lauric-N-methylglucamide

The phase behaviour of the middle‐phase microemulsion for the quaternary system lauric‐N‐methylglucamide (MEGA‐12)/n‐butanol/alkane/water has been studied with Winsor type, δ‐γ fishlike and novel ε‐β fishlike phase diagrams. A series of phase inversions Winsor I ( )→III (3)→II ( ) were observed for the three kinds of phase diagrams. The phase types, the phase volumes and the range of alcohol concentrations from the beginning to the end of the middle‐phase microemulsion were obtained from Winsor phase diagram. From δ‐γ fishlike phase diagram, the physicochemical parameters, such as the mass fraction of n‐butanol in the hydrophile‐lipophile balanced interfacial layer, A^S, the coordinates of the start and end points of the middle‐phase microemulsion, and the solubilities of MEGA‐12 and n‐butanol in alkane phase were calculated. The novel ε‐β fishlike phase diagram was also presented. From this kind of diagram, the above experimental phenomena were observed and the physicochemical parameters were calculated precisely. The novel fishlike phase diagram has advantages over the Winsor and δ‐γ fishlike phase diagrams in the evaluation of the solubilization power of the microemulsion and calculation of the related physicochemical parameters.