Studies of the viscosity and sedimentation of suspensions. Part V. The viscosity of settling suspensions of spherical particles

Abstract

After a brief review of the relative viscosity/volume concentration relationships which have been suggested for suspensions of smooth spheres, the results of new experimental work on rigidly defined systems of methyl-methacrylate spheres suspended in aqueous solutions are described and discussed. It is shown that, although their relative viscosity is independent both of the viscosity of the suspending liquid and the absolute size of the spheres at a given concentration, it is a function of their size distribution, decreasing with increasing size range to a constant value. The proportionality constant between specific viscosity and volume concentration at infinite dilution varies from about 4.0 for a size ratio of 1: 1 to 1.9 for ratios exceeding 3: 1. When the suspensions consist of dielectric particles in a non-polar liquid, electrostatic charging of the particles may affect the measured viscosity.