Thermodynamic Properties of Platinum Chloride Complexes in Aqueous Solutions: Derivation of Consistent Parameters from Literature Data and Experiments on Pt(cr) Solubility at 400-475A°C and 1 kbar

The solubility of Pt-(cr) in acidic chloride solutions was measured at 400-475A degrees C and P = 0.8-1.0 kbar using an autoclave technique and the analysis of the dissolved component after quenching. The PtCl (3) (-) complex was identified as the main Pt species at experimental parameters, m(NaCl) = 0.1-3.0 mol/kg H2O and m(HCl) similar to 0.01. The thermodynamic parameters of the Helgeson-Kirkham-Flowers (HKF) model were determined for Pt2+ and Pt-Cl complexes (PtCl (n) (2-n) n = 1-4) by analysis of literature data and their adjustment with obtained results. The solubility of Pt under supercritical P-T parameters calculated using these parameters is similar to Pd solubility. The thermodynamic properties and HKF model parameters for aqueous species determined in this study were incorporated into the on-line version of the FreeGC database ( http://www-b.ga.gov.au/minerals/research/methodology/geofluids/freegs_about.jsp), which allows calculation of the Gibbs free energy of system components and equilibrium constants of reactions with these species.