A generalised multicomponent thermodynamic model applied to the (NH₄)₂SO₄H₂SO₄H₂O system to high supersaturation and low relative humidity at 298.15 K

A mole fraction-based multicomponent thermodynamic model, previously applied to the system H₂OH₂SO₄, is here extended to mixtures with (NH₄)₂SO₄ at 298.15 K. Model parameters are determined by fitting to vapour pressure data (from isopiestic and electrodynamic balance studies), together with degrees of dissociation of the bisulphate ion and salt solubilities (solid phases (NH₄)₂SO₄, (NH₄)₃H(SO₄)₂ and NH₄HSO₄). The model successfully represents the thermodynamic properties of the system to high supersaturation over the full range of composition from (NH₄)₂SO₄H₂O to H₂SO₄H₂O. Equilibrium vapour pressures of NH₃ have been calculated for mixtures of various compositions. © 1995.