Abstract

This article explains the fundamental principles and practical aspects of the three steps in making a good dispersion: wetting the dry powder into the liquid, breaking up the wetted clumps, and preventing reagglomeration of the dispersed particles. It describes a variety of techniques for wetting powders into liquids of low, medium, and high viscosity, noting the design elements that provide effective operation. Simple equations illustrate how particle attractions and repulsions are related to basic physical forces and how the forces may be modified by changes in the chemical environment or by adsorption of dispersants. Several unusual methods of stabilizing dispersions are noted. Finally there is a brief section on evaluating the degree of dispersion, with reference to numerous standard methods, guidance for selecting a method appropriate to the need, and warnings of difficulties that limit the application of the methods.