A method is introduced to allow the calculation of differential diffusion coefficients from integral diffusion coefficient data collected with diaphragm cells below 0 degrees C. The method is demonstrated with concentrated potassium hydroxide diaphragm cell data at -15 degrees C and with published data from Stokes. Differential diffusion coefficients, calculated using Stokes＇ method and the proposed method, are compared for the HCl-water system at 25 degrees C.