Cellulose acetate membranes (2.5 acetyl groups per glucose unit) have been cast from acetone solutions, from acetone/formamide solutions and from acetone/water solutions with and without complete evaporation before swelling and with or without thermal curing. Then, the membranes have been characterized electrochemically by EMF-measurements. EMF measurements on dense cellulose acetate membranes (with complete evaporation) are repeatable to within + 5 mV, and all the conclusions drawn earlier from measurements on a single membrane specimen are generally valid for dense membranes. The variation of the parameters with the cation (Li-f, Na+ or K + ) found at pH(conc) = 5 is even more consistent than found earlier, since the pH was fixed exactly by dilution and not measured by a glass electrode. Predictions of EMF-values for mixtures of three electrolytes (LiCI, NaCl and HCI) are in aggreement with experimental values. With complete evaporation, the asymmetry may be kept below +1 mV for the dense membranes. The asymmetric membranes (incomplete evaporation) have a considerably larger EMF asymmetry (up to ± 7 mV), but the model used for dense membranes work well on the mean values. The asymmetric membranes are more swelled. Accordingly, a smaller value of the fixed charge density is found, and the ratios of diffusion coefficients are close to values in pure water. Except for the asymmetry, the skin layer does not seem to be of importance for the mean EMF-values of the membranes. Heat curing has no influence on EMF-values.