Simple electrical plateout method for measuring charge/mass of nonaqueous suspensions

Abstract

A simple method for the measurement of the charge/mass ratio of charged particles suspended in insulating fluids is described. The technique is based on the observation of the current or charge associated with the motion of charged particles and ions in a planar capacitor having one electrode overlaid with a collection sheet. The mass of the particles which are plated out is determined gravimetrically. The notable features of this method are: a one-dimensional cell with transparent electrodes which permit optical measurement of particle transit times, complete particle sweepout, and the detection of the initial current. As a result particle mobility and size, concentration and mobility of counterions, and the concentration of excess ions can also be determined. The method was tested at different plateout voltages, cell thicknesses, and particle concentrations and applied to a large number of nonaqueous suspensions with charge/mass ratio differing by 10 3. It is pointed out that the transport of charged species in these systems is space charge limited except at high electric fields, small cell thicknesses, and low charge concentrations.