Zones of sparingly soluble inorganic salts with membrane properties in gels

Article abstract of DOI:10.1002/bbpc.198800366

Polyacrylamide gels containing potassium oxalate (sodium oxalate) are brought into contact with aqueous solutions of Pb(NO₃)₂, CaCl₂, SrCl₂ and BaCl₂ respectively. The electrolyte concentrations in the gel phase and in the solutions are varied systematically. There exists a system specific characteristic concentration c_s below which advancing precipitation zones of PbOx, CaOx, SrOx, and BaOx (Ox: oxalate) within the gel are observed. The experiments indicate that the precipitation zones with membrane properties are generated by homogeneous nucleation. The kinetics of formation of oxalate precipitates in cellophane skins is studied by measurement of the membrane potential as function of time. In these systems precipitate is formed by interdiffusion of two solutions containing the appropriate ions.