Abstract
Electrophoretic measurements were carried out as a function of pH for various fractions of an acidic crude oil dispersed in pure water and low salinity solutions of NaCl and CaCl2. The acidic and basic components were selectively extracted from the crude oil in order to elucidate their importance for the interfacial charges and implicitly the zeta potentials. Ionization of basic and acidic components at low and high pH, respectively, could not fully account for the obtained zeta potentials. The results could, however, be explained by additional consideration of interfacial hydroxide ions, coming from the water phase.