Stability of dispersions in polar organic media. I. Electrostatic stabilization

Abstract

Electrostatically stabilized sols of silver, silver iodide, α-goethite, and copper phthalocyanine in methanol, ethanol, isopropanol, and acetone have been prepared and characterized. Coagulation concentrations with electrolytes of various charge numbers have been determined in water, in organic solvents containing 0.5% water, and in mixtures of water and ethanol or acetone of various compositions. Coagulation by monovalent counterions is due to compression of the double layer. With bi- and multivalent counterions coagulation is primarily caused by charge neutralization (equivalent coagulation) in media with a high content of the organic solvent, but by compression of the double layer in water-rich media. Charge reversal by bi- and trivalent cations and restabilization of the positive sol have been found for the silver sol in ethanol.