Strong and weak points in the interpretation of colloid stability

Lyophobic dispersions can be stabilized against aggregation by electrostatic repulsion or by “steric” repulsion caused by the presence of large molecules at the interfaces. Theories of colloid stability are briefly reviewed.Strong and weak points in the present interpretations are pointed out. Two important weak points in the interpretation of electrostatic stabilization are: 1) the assumption that the zeta potential and the Stern potential are about identical, and 2) the apparent lack of influence of the particle size on the rate of slow coagulation.A list of areas where new experiments and/or further development of theories are expected to be profitable closes the paper. In several of these areas a combination of a fluid mechanical and a colloid chemical approach is called for.