Co-Crystallization in systems with carnallite-type double salts

The RbCl · MgCl₂ · 6H₂O? NH₄Cl · MgCl₂ · 6H₂O? H₂O and CsCl · MgCl₂ · 6H₂O? NH₄Cl · MgCl₂ · 6H₂O? H₂O systems have been investigated at 50°C. The formation of continuous series of mixed crystals is observed. An almost complete coincidence of the distribution coefficients values of the components between the solid and liquid phases determined experimentally and calculated theoretically using only solubility data for the two double salts has been established. The 2 RbCl · CoCl₂ · 2H₂O? RbCl · MgCl₂ · 6H₂O? H₂O system has been studied at 25°C. It has been established that this system belongs to the simple eutonic type. The two double salts form no mixed crystals between each other. This fact is explained by the different character of the metal-ligand interaction of Mg²⁺ and Co²⁺ ions in aqueous halide systems.