Heterogeneous equilibrium in the quinary system of NaCl-KCl-MgCl₂-CaCl₂-H₂O at 25°C was investigated to get the basic data for the graphical computation of the concentration process of ion exchange membrane brine, the treatment of its bittern and the preparation of the enthalpycomposition diagram.
On the basis of the solubility data and those available from the existing literatures, an equilibrium diagram of the five-component system at 25°C was prepared. Also, simplified diagrams were drawn with the data for those points saturated with NaCl for ease of practical computation.
Solubilities of NaCl available at the univariant system (four solids and one solution phase) and at the bivariant (three solids and one solution phase) were found to be very small, ranging from 0.1 to 0.15 wt.%. The diagram saturated with NaCl was found nearly the same as that of the four-component system KCl-MgCl₂-CaCl₂-H₂O, because NaCl could form neither double salt nor solid solution with the other salts in this system.