Activity coefficients in (hydrogen bromide + magnesium bromide)(aq) at several temperatures. Application of Pitzer's equations☆

Abstract Activity coefficients of HBr in (hydrogen bromide + magnesium bromide)(aq) have been determined at constant total ionic strengths of (0.1, 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0) mol · kg −1 . Temperatures ranged from 278.15K to 318.15K at 5K intervals. Electromotive-force measurements were made on the cell without liquid junction: Pt|H 2 (g,p = 101.325 kPa )| HBr (m A ), MgBr 2 (m B )| AgBr(s)|Ag(s) The results have been interpreted using Harned's equations and the more comprehensive treatment of Pitzer. Activity coefficients for HBr in the salt mixtures obey Harned's rule at all ionic strengths studied. The Pitzer mixing parameters S θ H, Mg and ψ H, Mg, Br (including higher-order electrostatic effects) and θ H, Mg and ψ H, Mg, Br (excluding higher-order electrostatic effects) as well as the temperature derivatives of the mixing coefficients have been determined. Trace activity coefficients for HBr and MgBr 2 have also been calculated.