MULTIPLE ION ASSOCIATION IN SUPERCRITICAL AQUEOUS-SOLUTIONS OF SINGLEELECTROLYTES

Solute speciation in supercritical aqueous alkali metal halide solutio ns plays an important role in various industrial and natural processes , for example, corrosion of metals, solvent extraction, crystal growth , metamorphism, and the formation of hydrothermal ore deposits. To bet ter characterize such speciation, degrees of formation of polyatomic c lusters of sodium and chlorine ions have been computed with the aid of dissociation constants generated from Monte Carlo calculations which are consistent with both supercritical conductance measurements and el ectrostatic theory. The calculations indicate that the solute in alkal i-halide solutions is successively dominated by increasingly complex p olyatomic clusters as the solute molality increases at pressures and t emperatures where the dielectric constant of water is less than or sim ilar to 15.