1. (in an ion exchanger) the mobile exchangeable ions.
    PAC, 1993, 65, 819 (Nomenclature for chromatography (IUPAC Recommendations 1993)) on page 854
  2. (in colloid chemistry) ions of low relative molecular mass, with a charge opposite to that of the colloidal ion.
PAC, 1972, 31, 577 (Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry) on page 607