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Electrostatic parameters in the Debye-Hiickel equations for activity coefficients and the relative partial molal enthalpies, internal energies, isochoric and isobaric heat capacities, volumes, comprcssibilities, and expansibilities of aqueous electrolytes have been computed for pressures and temperatures from l bar to 5 kb and 0° to 600°C. The calculations are based on the equation of state for H 2 0 derived by Keenan and others (1969) for pressures ~ a kilobar together with power functions of temperature and density (or pressure) obtained by regression analysis (Helgeson and Kirkham, l974a) of dielectric constant data (Oshry, ms; Owen and others, 1961; Heger, ms) and finite difference coefficients of isobaric thermal expansion and isothermal compressibility generated (Helgeson and Kirkham, l974a) from densities (Burnham, Holloway, and Davis, 1969) of H 2 0 at pressures > a kilobar. The Debye-Hiickel parameters are sensitive quasi-asymptotic functions of pressure and temperature, which may be monotonic or exhibit extrema, depending on the property. Changes in the dielectric constant and the Debye-Hiickel parameters with increasing temperature andfor decreasing pressure favor increasing mineral solubilities and extension of the applicability of Debye-Hiickel theory to electrolytes with progressively higher concentrations. In the supercritical region, the absolute values of the limiting law parameters for the relative partial molal properties of electrolytes are of the order of 5 to > 1000 times larger than they are at 25°C and l bar.

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