Double Membrane Diaphragm Technique for Absolute Measurements of Diffusion Coefficients

Abstract

A new technique for measuring diffusion coefficients utilizing two thin porous membranes separated by a spacer of known cross-sectional area and thickness is presented. The method permits absolute measurements of diffusion coefficients of chemical and biological materials in solution. The technique is based on the free-diffusion space between two membranes, thus avoiding the problems of solute-membrane interactions and tortuosity of the pore space that are present with single membrane diaphragms. Diffusion coefficient measurements of 5 x 10~4 M NaCl and 5 x 10-4 M KC1 arc in good agreement with values reported in the literature