Equations of state for electrolyte solutions
Thermodynamic Modelling of Electrolyte Solutions

In theory, equations of state are the most versatile thermodynamic models in terms of the systems that can be handled: the same model can be used to represent the properties of both liquid and vapor phases, pure bodies and mixtures, over a wide range of pressures and compositions. They include a reduced number of parameters needed to describe a system, and most of these parameters have a physical meaning. Activity coefficient models (see § 3