Thermodynamics of hydrothermal systems at elevated temperatures and pressures

Sufficient thermodynamic data are available to permit calculation of equilibrium constants for a large number of hydrothermal reactions. Where the data are incomplete, the calculations involve entropy estimates, application of average heat capacities, and/or assumptions concerning the temperature dependence of thermodynamic variables and the relative importance of electrostatic and non-electrostatic interaction among the species. Temperature stoichiometric activity coefficients for individual ions can be calculated using deviation functions computed from osmotic coefficients for concentrated NaCl solutions. The results of such calculations, together with computed heat capacities, enthalpies, entropies, and equilibrium constants for many hydrothermal species and reactions are presented in tables and diagrams.