Pseudo-ternary phase diagrams in four-component system of cetyltrimethylammonium bromide/n-butanol/n-heptane/water (CTAB/n- C_4H_9OH/n-C_7H_(16)/H_2O) are presented. The influence of cosurfactant- to-surfactant mass ratio, k_m = W(C_4H_9OH)/W(CTAB), on the size of the microemulsion region in the title system is discussed. The apparent diffusion coefficients D_(app), of several microemulsion samples were measured by using ferrocene (Fc) as the electroactive probe by semidifferential electroanalysis. The microstructure and the structural conversion of the microemulsion has been determined from the water content dependence of the apparent diffusion coefficients in one-phase microemulsion region. The electrical conductivity datum supported the results of the semidifferential electroanalytical measurement.

Key words: CTMAB, MICROEMUSION, ELECTRICAL CONDUCTIVITY, N-BUTANOL, HEPTANE, WATER, PHASE DIAGRAM, FERROCENE, DIFFUSION COEFFICIENTS