THE STRUCTURE OF THE COLLODION MEMBRANE AND ITS ELECTRICAL BEHAVIOR XI. Tm~ PREPARATION AND PROPERTIES OF "MEGAPERMSELECTIVE" COLLODION MEMBRANES COMBINING EXTREME Iomc SELECTIVITY WITH HIGH PERMEABILITY BY CHARLES W. CARR Am>

The classical investigations of Michaelis and collaborators 1 on the dried collodion membrane as well as the work of other investigators have revealed the basic physicochemical properties of membranes of porous character which are selectively cation-permeable. Dried collodion membranes prepared from suitable collodion ~-4 were found to allow the cations of uni-univalent strong inorganic electrolytes in solution to pass through, whereas these membranes are almost impermeable to anions. This ionic selectivity has been shown to be due. to the negative electrical charge of the membranes arising from the presence of dissociable acidic groups on the pore walls. 4-e The further study of the basic physicochemical properties of these membranes is impeded by certain unfavorable features, and their use in model systems is still more restricted for the same reasons. The electromotive properties of many of these membranes except in very dilute solutions do not approach the theoretically possible maximum values as closely as would be desirable; moreover they deteriorate during prolonged experiments. Their absolute permeability for non-electrolytes is very small, their ohmic resistance is very