MULTIPLE ION ASSOCIATION IN SUPERCRITICAL AQUEOUS-SOLUTIONS OF SINGLE ELECTROLYTES

Solute speciation in supercritical aqueous alkali metal halide solutions 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 better characterize such speciation, degrees of formation of polyatomic clusters 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 electrostatic theory. The calculations indicate that the solute in alkali-halide solutions is successively dominated by increasingly complex polyatomic clusters as the solute molality increases at pressures and temperatures where the dielectric constant of water is less than or similar to 15.