Re-evaluation of the Thermodynamic Activity Quantities in Pure Aqueous Solutions of Chlorate, Perchlorate, and Bromate Salts of Lithium, Sodium or Potassium Ions at 298.15 K

Abstract

The Huckel equation used to correlate the experimental activities of dilute alkali metal chlorate, perchlorate or bromate solutions up to a molality of about 1.5 mol⋅kg−1 contains two electrolyte-dependent parameters: B {that is related closely to the ion-size parameter (a∗) in the Debye–Huckel equation} and b1 (this parameter is the coefficient of the linear term with respect to the molality, which is related to hydration numbers of the ions of the electrolyte). In more concentrated solutions up to 7 mol⋅kg−1, an extended Huckel equation was used, it contains additionally a quadratic term with respect to the molality, and the coefficient of this term is the parameter b2. Parameters for the Huckel equations were evaluated from isopiestic data for LiClO3, LiBrO3, LiClO4, NaClO3, NaBrO3, NaClO4, KClO3, and KBrO3. In these estimations, the Huckel parameters determined recently for NaCl solutions were used. The resulting parameter values were tested with the vapor pressure and isopiestic data available in the literature for solutions of these salts. Most of these data were reproduced within experimental error by means of the Huckel or extended Huckel equations, at least up to a molality of 3.0 mol⋅kg−1, for all salts considered. Reliable activity and osmotic coefficients for solutions of these salts can, therefore, be calculated by using the new Huckel equations, and they are tabulated here at rounded molalities. The activity and osmotic coefficients obtained from these equations were compared to the values reported in several previous tabulations.