ACTIVITY AND SPECTROSCOPIC ANALYSIS OF CONCENTRATED-SOLUTIONS OF K2S

The determination of activity of highly concentrated sulfide solutions is important for the thermodynamic analysis of speciation. A novel '' evanescent'' method for solvent analysis and determination of mean sol ution activities is applied to measure the first activity coefficients of highly concentrated sulfide solutions. Another technique, submicro meter path length spectroscopy, provides in situ observations of the p roblematic alkaline sulfide equilibria in the domain of highly concent rated sulfide. Combined, these methods provide an upper bound estimate for the second acid dissociation equilibrium of hydrogen sulfide of p K(2) > 17.3(+/-0.1) and the free energy of formation far sulfide of De lta G degrees (S2-)(aq) > 111 (+/-0.5) kJ/mol.