Mechanism of ion exchange in crystalline zirconium phosphates. X. Calorimetric determination of heats of sodium(1+) ion-proton exchange Academic Article uri icon


  • The heats of Na+-H+ exchange on three samples of zirconium phosphate of widely different crystallinities have been determined calorimetrically. For the crystalline sample the first 50% of exchange is exothermic with ΔH° = -6.90 ± 0.10 kcal/mol. The second half of the reaction is endothermic with ΔH° = +6.45 ± 0.15 kcal/mol. The corresponding entropies accompanying these reactions are -31.0 ± 0.1 and 0.0 ± 0.1 eu. In the case of a gelatinous, nearly amorphous, exchanger the reaction is initially exothermic but then the heat function passes through a broad maximum and becomes progressively more endothermic. The overall reaction is endothermic with ΔH° = 2.0 ± 0.2 kcal/mol and ΔS° = -14.8 ± 1.3 eu. The semicrystalline exchanger exhibited heat effects surprisingly similar to those of the fully crystalline exchanger. Qualitative explanations for the observed results are presented.

author list (cited authors)

  • Clearfield, A., & Kullberg, L. H.

citation count

  • 17

publication date

  • January 1974