Diffusion of benzene, phenol and resorcinol in propane-1,2-diol, and the validity of the Stokes-Einstein equation

Abstract

An improved method for establishing a concentration gradient in a thin, horizontal, liquid film by thermal diffusion is described. When the decay of this concentration gradient was followed by Savart plate interferometry, it was found possible to measure diffusion coefficients as low as 5 × 10^–12 m² s^–1 with reasonable precision. When the method was applied to dilute solutions of benzene, phenol and resorcinol in propane-1,2-diol, the results showed the importance of solute-solvent interactions in affecting the value of the mutual diffusion coefficient for the system. The possible importance of these observations in the interpretation of rate constants observed for bimolecular diffusion-controlled reactions is discussed.