Precipitation membranes - A review

Precipitation membranes are generated exclusively by diffusion-controlled precipitation. They form an asymmetrical barrier with an electrical polarity. Their electrical charges, which are charges of adsorbed ions, are not fixed and can easily and reversibly be desorbed. In the conditioned state a relatively large potential difference develops, the membranes rectify electrical current and display specific ion permeabilities. A unique property of these membranes allows determination of the permeability of single ionic species. The permeability of OH^- was thus found to be markedly greater than that of H⁺, Precipitation membrane effects may be involved in rectification phenomena in biological membranes such as the frog skin.