The initial mass transfer rate of acetic acid from the aqueous to the organic phase with tri-n-octylamine and toluene or isododecane as solvents has been studied in a constant interfacial cell area as a function of the stirring speed, concentrations of the transfer species, and the influence of chemical adsorption layers. For a detailed understanding of the mass transfer process, the electrophoretic mobility of oil-in-water droplets for these systems has been measured with a ZETA-sizer. The electrophoretic mobilities of the different reactive extraction systems were investigated for their dependence on the pH value and with different interfacial charges. It was proved that a change of the interfacial charge influences the zeta potential of the dispersed oil drops in the same way as the reaction kinetics, and thus the mass transfer of acetic acid.