Enhanced Salt Diffusion along the Border-line of Mosaic Permselective Membranes

Abstract

AN ideal permselective membrane between, for example, a salt solution and water only allows its counter-ions to pass at the moment of immersion. The ions which have passed are attracted to the surface by their partners of opposite charge which remained on the other side: both sides of the membrane become charged and under ideal conditions the Nernst potential is established. This prevents further counter-ions from passing the membrane so that no actual diffusion of salt takes place. The samo holds true for a membrane of opposite charge, only the signs are reversed. However, at the border-line between two permselective membranes of opposite sign a new situation has to be expected. Anions and cations respectively are present on the two sides of the borderline. Here they eliminate, or in any event weaken, the potential difference in the neighbourhood of the border because they neutralize each other's charges. Thus it should be possible for further anions and cations to pass across their respective, adjacent, domains. Actually salt should diffuse across the membrane along the borderline, anions and cations passing through beside each other on both sides of the border.