Valence and nature of exchanging ions:

a) At low aqueous(less than 0.1 N) concentrations and ordinary temperatures the extent of exchange increases with the increasing valency of the exchanging ion, i.e., Na⁺ < Ca²⁺< Al³⁺< Th⁴⁺

This means in which divalent ions are more tightly held through the resin than monovalent ions and trivalent ions more tightly than divalent ions.

b) Under similar conditions and constant valence, for univalent ions the extent of exchange decreases with the size of hydrated cation. therefore,

Li⁺< H⁺ < Na⁺ <NH ⁺ < K⁺ <Rb⁺ <Cs⁺ < Tl⁺ < Ag⁺

c) In the case of divalent ions, the ionic size is an important factor but the incomplete dissociation of salts plays an important part.

Cd²⁺ < Be²⁺ < Mn²⁺ < Mg²⁺  ≈ Zn²⁺ < Cu²⁺  ≈ Ni²⁺ < Ca²⁺ < Sr²⁺ < Pb²⁺ < Ba²⁺

d) With strongly basic anion exchange resins ( Dowex 1 and 21 K), univalent anions appear to behave similarly to univalent cations.

F^- < OH^-< CH₃COO^-< HCO₃ ^- < Cl^-< HSO₃ ^-  ≈ HSO₄ ^- < CN^-< Br^-< NO₃^- < I^-

For Dowex-2, OH^- falls between HCO ^- and Cl^-.