Complex formation in molten salts. Association constants of lead halide complexes in molten KNO3–Ba(NO3)2 eutectic as solvent

Abstract

Thermodynamic association constants and specific Helmholtz free energies for the formation of the species PbX⁺, PbX₂(X = Cl, Br or I) in dilute solutions of Pb(NO₃)₂ and KX in molten KNO₃–Ba(NO₃)₂(87.6:12.4 mol %) in the temperature range 568.2–628.2 K are reported. An e.m.f. method involving measurements of activity coefficients of (K,Ba) X and Pb(NO₃)₂ using Ag,AgX(s) and Pd–PdO–PbO indicator electrodes, respectively, was employed. Data did not suggest the formation of the dinuclear species. Applicability of the quasi-lattice model equations in predicting temperature coefficients of association constants in the above temperature range has been examined.