Specific ion effects: Why colloid science has failed to contribute to biology

Abstract

Surface tension of salt solutions and double layer forces between charged interfaces show marked specific ion effects not accommodated by the classical double layer theory for charged interfaces. We will demonstrate how this can be partly remedied when the ionic dispersion potential that acts between ion and interface is included on the same level as the electrostatic potential. We will focus on the important influence of these dispersion forces on ionic distributions near air-water and mica-water interfaces. Dispersion potentials that accommodate the experimental surface tension of KBr also gives the physical reason why Pashley et al. had to postulate a 90% binding of bromide ions to the charged mica surfaces to explain their measured force.