Problems of stability in hydrophobic colloidal solutions, I. On the interaction of two colloidal metallic particles. General discussion and applications

Abstract

The problems in colloid science may be divided into two main groups. The first, and more fundamental one, deals with the interaction of a single colloidal particle with its surrounding dispersion medium. This includes the basic question of the relation between the concentration of electrolyte present and the amount of adsorption of ions on the surface of the particles in a lyophobic sol. A knowledge of this relation will determine the charge on the particle as a function of the two chief physical quantities that may be varied experimentally, the radius of the particle (which we assume to be spherical) and the concentration of electrolyte. In this paper we shall not be concerned with this problem but rather assume that this dependence of the charge is known. Practically all other phenomena in sols, forming the second group, may be attributed to the nature of the repulsive and attractive forces acting between the particles. Among these are the general problems of stability, including the phenomenon of slow and fast coagulation, reversible and irreversible flocculation and such properties as the Schultz-Hardy rule for hydrophobic sols and the deviation of the osmotic pressure from the ideal law. Since most hydrophobic sols have a low concentration of particles, all these properties should be explicable in terms of the interaction of two particles only.