ISL Equilibrium Calculator is a command line based interface software, and mainly using for solid-liquid equilibrium calculation involving electrolyte aqueous system, e.g. seawater system, salt lake brine system, underground brine system, and industrial waste water system.
In the software, Harvie extended Pitzer's model has been used as the electrolyte aqueous solution model (for details, you can see Harvie & Weare1980,1984 and 1987). For solving solid-liquid equilibrium of a given system including water and some kind salt only, Gibbs free energy minimization procedure has been implemented. As we known, Gibbs energy minimization(GEM) procedure is a optimization procedure in mathematics aspect. For solving constrained optimization problem, there are many many method, which include determined methods and stochastic methods. In 1980, Harvie&Weare used a Newton type method for calculating solid-liquid equilibrium, and in 1987, they gave the method in details. In ISL Equilibrium Calculator, we used a Particle Swarm Algorithm to solve the Gibbs energy minimization problem.
ISL Equilibrium Calculator is a databank based software also, like EQ3/6. The databank file is independent with the program, so users can modify the databank file, or create his/her own databank if necessary. And there is no need to modify the source code. All the databank files in the source code(islec-x.x.x/databank/) have been tested, and the results are putted in the directory(islec-x.x.x/test/). For every sub-system, there is a validation plot, where calculated values and experimental values are plotted together. But it is noticeable, we are not sure the experimental data used is accurate or not.