Well-known non-ideal models for aqueous electrolytes properties have been included in the new Aqua module. The activity coefficient models include the extended Debye-Hückel model here called Davies model, Pitzer model, and Harvie’s modification. An extensive database including about 1000 Pitzer parameters for different systems have been collected to date. The Pitzer parameter database currently has 407 cation-anion pairs, 102 cation-cation and anion-anion pairs, 114 ternary coefficients, and 289 ion-neutral pairs. Many of these parameters are tabulated as temperature-dependent functions. The user is given the option to choose between simpler and more rigorous models and to select the number of parameters used.
In the HSC Aqua module, the Water Phase sheet is used for calculating the activity coefficients, enthalpies and heat capacities for homogeneous (single phase) aqueous systems. The user specifies the system by inserting the ionic or molecular formulas of the solute species in the SPECIES Formula column, the temperature in the Temp oC column, and the amounts in the Amount kmol column.