Stability of non-aqueous dispersions. I. The relationship between surface potential and stability in hydrocarbon media

The electrophoretic mobility of rutile has been related to the stability of its dispersions in solutions of Aerosol OT (sodium di-2-ethylhexyl sulfosuccinate) in p-xylene over a range of surfactant concentrations. For comparison purposes similar experiments have been carried out with α-alumina, the carbon black Vulcan R, and a copper phthalocynanine green pigment. Zeta potentials in excess of 50 mv. were found to be necessary for long-term stability, and this is in good agreement with theoretical predictions for the size of aggregate found in the stable dispersions. Addition of water to the rutile system has shown its importance in determining the sign and magnitude of the surface potential.