CURRENT STATE OF KNOWLEDGE ON THE SPECIATION OF HYDROTHERMAL SYSTEMS

The main methods for the experimental determination and estimation of speciation in aqueous solutions under hydrothermal conditions are cons idered. It is shown that, in aqueous solutions of moderate concentrati on, the thermodynamic properties of aqueous species are satisfactorily described on the basis of the electrostatic model. To describe the th ermodynamics of aqueous species in concentrated solutions, models of a ctivity coefficients, extended in comparison with the Debye model, wer e proposed along with statistical physics methods and direct (spectros copic) determination of component states.