Solid–liquid equilibria in the quinary system LiCl–KCl–RbCl–MgCl2–H2O at T = 323 K

• Phase equilibria involving rubidium chloride in water–metal chlorides system.
• The carnallite type double salt and solid solution were found in the system.
• Salt [(K,Rb)Cl] can be more easily separated from solution than the other coexisting salts in this system at 323 K.

The mixed aqueous electrolyte system containing the chlorides of lithium, potassium, rubidium, and magnesium has been investigated using the method of isothermal evaporation at 323 K. The space diagram, the planar projection diagram and the water content diagram have been constructed based on the Jänecke method. There are six invariant points, eighteen univariant curves, and eight crystallization fields corresponding to single salts lithium chloride monohydrate (LiCl·H2O), bischofite (MgCl2·6H2O), a solid solution of potassium and rubidium chloride [(K,Rb)Cl], and carnallite type double salts LiCl·MgCl2·7H2O, KCl·MgCl2·6H2O, and RbCl·MgCl2·6H2O in the space diagram. With a view to the crystallization zones, the crystallization zone of salt [(K,Rb)Cl] occupies the largest part, meaning [(K,Rb)Cl] can be more easily separated from solution than the other coexisting salts in this system at 323 K.

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