Hydrothermal brines, seawater systems, evaporite formations and industrial salt recovery technology require a detailed knowledge of the thermodynamic properties of aqueous solutions. In fact, evaporation is a major process in and environment; dilute solutions are evaporated until saturation and then various minerals crystallise. Tunisian salt lakes (called Sebkha and Chott) represent an important resource of oceanic salts which have a great role in the economic and agricultural sectors. In our case, from the above-mentioned sources, we extract a natural brine highly concentrated with Na, Mg2+, K+, Cl- and SO42- ions. Many authors treated these concentrated solutions as a reciprocal quinary system(class II) Na+, K+, Mg2+/Cl-, SO42- - H2O. In previous works, we met difficulties when using the classic geometrical representations of this system due to the information loss (5 degrees of freedom and 3D space representations). Consequently we decided to resort to the computer for help. For this purpose the DPAO method is employed to simulate brine evaporation and to predict the solid phases deposited during the process. The DPAO method unwinds in two stages: Systematic classification of data, which is the aim of this paper. Crystallization path representation, applying the phase rule and performing a mass balance for each step. The computer allows the hyperspace calculation of all components; therefore the method has the universality character. (C) 2003 Published by Elsevier Science Ltd.
