A coherent, systematic approach for the determination of solid-liquid phase behavior of a multi-component salt lake system for use in the synthesis of crystallization process is presented. It centers on the thermodynamics of such a salt lake system and integrates three interrelated activities-representation of the system phase behavior as a phase diagram/thermodynamic model, experimental determination of the necessary data and visualization of the relevant crystallization regions. To illustrate this approach, the thermodynamics of a simplified salt lake system Li+, Na+, K+, Mg2+// Cl-, SO42- H2O at 25 degrees C and 1 atm was determined. The identification of process alternatives using the resulting phase diagram for recovering Li2SO4 center dot H2O was also illustrated. (c) 2008 American Institute of Chemical Engineers.