A three-parameter EoS to describe aqueous non-electrolytes at infinite dilution over a wide range of state parameters, with preliminary application to 1:1 electrolytes

A new equation of state (EoS) for describing the thermodynamic properties of aqueous non-electrolytes at infinite dilution is proposed. It is based on the accurate EoS for the solvent (H2O) given by Hill [21], it requires only three empirical parameters to be fitted to experimental data, and these are independent of temperature and pressure. Knowledge of the thermodynamic properties of the pure gas, together with these three parameters, enables prediction of the whole set of thermodynamic properties of the solute at infinite dilution (chemical potential, entropy, molar volume, and apparent molar heat capacity) over a wide range of temperatures (0–500 °C) and pressures (1–2000 bar), including the near-critical region. In the cases where experimental thermodynamic data are lacking, the empirical parameters can be estimated solely from the known standard-state properties of the solute. The proposed approach has been tested for non-polar (Ar, Ne, H2, N2, O2, CO2, H3BO3), polar (H2S, NH3) dissolved molecules, ion pairs (HCl, HF), and aqueous hydrocarbons (CH4, C2H4, C2H6, C3H8, C4H10, C6H6). Some preliminary calculations show that the approach also has promise for the description of electrolytes.