Electric birefringence evaluation of particle size distributions: theory for polydisperse equivalent spheres

Abstract

Electric fields induce orientational order in particulate suspensions thereby rendering them birefringent. The decay rate of the birefringence following the field termination is characteristic of sample size, shape, and polydispersity. Theory is developed herein for the evaluation of a two-parameter function for the distribution of sizes of arbitrarily shaped particles in terms of their equivalent spherical diameters. An experimental procedure, involving the measurement of the birefringence decay characteristics in two well-defined experimental conditions, is outlined and used to check the theory for a colloidal suspension of polytetrafluoroethylene particles in water.