The effect of the electric charge distribution on the ageing of an aerosol

Abstract

Smoke-chamber experiments have been carried out to determine the electric charge distributions and the constants descriptive of coagulation and surface loss of aerosols of porous silica powder, magnesium oxide and ammonium chloride. The data obtained were used to test the hypothesis that the rate of coagulation is affected by the electric charge distribution. Calculations have been made of the effect of electric charges on the particles of an aerosol on its rate of coagulation due to Brownian movement, differences in gravitational settling and turbulence. A simple expression for the coagulation constant was obtained which was found to be a function of the fraction of positive particles, the fraction of negative particles, the average particle charge of each sign and the average radius. A more exact treatment of ageing data than has previously been presented indicated a possible variation in the coagulation and surface loss constants with time, and this variation has been shown to be related to changes in the electric charge distribution.