Measurement of diffusion coefficients by means of cataphoresis

Abstract

A new measuring method for diffusion coefficients in gas mixtures is described, using the cataphoretic segregation. A DC-discharge in a gas mixture causes a segregation, which vanishes by diffusion after extinguishing the discharge. The diffusion coefficient can be calculated from the time dependence of the densities of the gas components. This time dependence can be measured mass-spectrometrically. The diffusion coefficient in a Ne-Ar-mixture as a function of temperature was determined between 300 and 650°K. The results were compared with diffusion coefficients calculated from viscosity data. Our results and those calculated from viscosity measurements are consistent in the considered temperature region.