A relation was obtained between electro-chemical properties of sodium salts (NaCl, NaBr, and Na2SO4), and the thermodynamic property of permeability in symmetrical cellulose acetate membranes, the distribution coefficient K and the kinetic property, the overall diffusion coefficients D. K and D were obtained by the method we proposed using measured unsteady- and steady-state dialysis data. The K values increase with the increase of water content and are in the range of 10(-2) for sodium halides and 10(-3) for Na2SO4. D is found to increase with the increase of the solute concentration, and the extrapolated values of D to zero concentration D-(0) are obtained as 0.015-0.03 mum(2)/s and increase with the increase of water content in the membrane. D can be divided into the concentration independent diffusion coefficients in the dense part of the membrane Dd and in the porous DP, applying a two-part (perfect or dense and imperfect or porous) model of the membrane. Contrary to D-d,D-p increases with the increase of W-w and can be correlated as D-p,D-c = (D) over bar (d) exp (gamma x W-w). It is shown that the averaged D-d, (D) over bar (d) increases with the increase of the quantity of the ionic mobility u(o) of the solutes at infinite dilution divided by valence, and that the parameter gamma increases with the increase of the ionic mobility u(o). The value of K increases slightly with the increase of water content and decreases with the increase of the Flory-Huggins parameter chi. The Flory-Huggins parameter chi is calculated from the measured values of distribution coefficients and data obtained from the literature. And it was found that the gradient of linear decrease of chi (lambda (cation)) depends on equivalent ionic conductivity of anion of salt, lambda (an).