Lyotropic sequences in colloid stability revisited

Lyotropic sequences for simple ions at water–solid interfaces are reviewed. Most informative are those systems for which data are available both for the stability and for the surface charge. Silver iodide and several oxides belong to this category. The collected evidence indicates that in most cases specific pair interaction between the ion and surface groups are responsible. Such interactions correlate similarly in aqueous electrolyte solutions. Gibbs energies are of the order of a few kT per pair, and are, to a large extent, entropically determined. As a novel element, dynamic lyotropic sequences are also discussed; they are reflected in the tangential mobility of bound ions. These mobilities are to a large extent controlled by the rapidity of exchange with the diffuse part of the double layer.