Electronegative, strong acid type, collodion-base membranes of extreme electrochemical activity were prepared by casting
membranes of any desired porosity from collodion solutions containing dissolved sulfonated polystyrene, or by the adsorption
of sulfonated polystyrene from aqueous solutions on preformed highly porous collodion membranes whose porosity can
subsequently be reduced to the desired degree by drying. The charge density on the walls of the pores of these membranes
can be adjusted at will. The membranes combine strong-acid character with the mechanical strength, flexibility and thinness
characteristic of collodion membranes. The membranes of high porosity show high anomalous osmotic activities in
solutions of acids as well as in neutral electrolyte solutions. The most useful permselective membranes give rise to concentration
potentials which agree with the calculated thermodynamic maximum potential in solutions of potassium chloride
and hydrochloric acid u to 0.1 N within the meaningfulness of the method. At higher concentrations the measured potential
becomes gradually Lss than the theoretical value. The ohmic resistances of the permselective membranes of highest
selectivity (as measured in 0.1 N KC1) may be adjusted from about 30 ohms cm.2 upward. In solutions of uni-univalent
electrolytes the more highly selective membranes have preferential permeabilities for cations which are 1000-2000 times that
for anions at 0.1 N; in more dilute solutions of uni-univalent electrolytes or in solutions of uni-divalent electrolytes the relative
permeability for cations may be many times greater. The general methods of making collodion-base membranes may be
applied to the preparation of membranes from a variety of combinations of structural high polymers and polyelectrolytes