Mutual solubility of ammonium perrhenate in solutions containing ammonium salts

Mutual solubility measurements were carried out for three multi-component systems of ammonium perrhenate (NH₄ReO₄) and one of the ammonium salts (NH₄NO₃, NH₄Cl or (NH₄)₂SO₄) dissolved in water. Experiments were carried out using the isothermal solution saturation method at 293.15K. The concentrations of the reagents in saturated solutions in each system were determined by analytical methods. On the basis of the results, the solubility isotherms were determined. The phase diagrams were prepared for each investigated system. The eutonic point and the solubility isotherms of both tested salts are marked on each phase diagram. The data provided were implemented to predict the composition of the solid phase in the purification process of crude ammonium perrhenate (CAP) by recrystallisation from solutions of ammonia salts. Moreover, the efficiency of salting-out for tested systems may be determined.