Measurement of Diffusion Coefficients of Binary Liquid Systems: The Moiré Pattern Method

Abstract

<p> A diffusion cell of the "shearing type" was used to diminish the effect of convection which is always present when two liquid phases are brought into contact with each other in a diffusion cell. Also a special optical arrangement was used to photograph the refractive index distribution of the system. For those systems with refractive index changing linearly with concentration, the concentration profiles were obtained and diffusion coefficients were calculated at different concentrations. </p> <p> This optical method gave only fair reproducibility- the deviation among diffusivities found for systems investigated varying from 3 to 10%- however, it permitted rapid analysis and on this basis is recommended for situations where speed is essential and high accuracy is not required. </p>