The ionization constant of water over wide ranges of temperature and density

Andrei V. Bandura, Serguei N. Lvov

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A semitheoretical approach for the ionization constant of water, K W, is used to fit the available experimental data over wide ranges of density and temperature. Statistical thermodynamics is employed to formulate a number of contributions to the standard state chemical potential of the ionic hydration process. A sorption model is developed for calculating the inner-shell term, which accounts for the ion-water interactions in the immediate ion vicinity. A new analytical expression is derived using the Bragg-Williams approximation that reproduces the dependence of a mean ion solvation number on the solvent chemical potential. The proposed model was found to be correct at the zero-density limit. The final formulation has a simple analytical form, includes seven adjustable parameters, and provides good fitting of the collected KW data, within experimental uncertainties, for a temperature range of 0-800°C and densities of 0-1.2 g cm-3.

Original languageEnglish (US)
Pages (from-to)15-30
Number of pages16
JournalJournal of Physical and Chemical Reference Data
Issue number1
StatePublished - 2006

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry


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