Electrical Conductance Behavior of Oil-in-Water Microemulsions Stabilized by Sodium Dodecyl Sulfate and 1-Butanol

Abstract

The specific conductivity of several oil-in-water (o/w) microemulsions (MEs) stabilized by sodium dodecyl sulfate and 1-butanol was measured at 25 °C as functions of the volume fraction of oil (φ0) and the molar ratio of water to surfactant (R). The oils used are octane, benzene, toluene, carbon tetrachloride, chloroform, cyclohexane, xylene, and nitrobenzene. The conductivity data were explained by the modified Bruggeman equation in the entire experimental range of φ0 in the case of octane and nitrobenzene and in a limited range of φ0 in the case of other oils. The value of the slope of this equation, f, is found to depend on (i) the concentration of surfactant or the R value, (ii) the nature of the oil, and (iii) the nature and number of substituents, if the oil is a substituted benzene. The specific conductivity data of o/w MEs of R = 120 and 100 were also analyzed in the light of the mixed electrolyte model, and the values of aggregation number, counterion binding constant, and radius of droplet were computed.