Production of Complex Hydrosulphates in the K3H(SO4)2–Rb3H(SO4)2 Series: II. Phase Equilibria in the K2SO4–Rb2SO4–H2SO4–H2O System

The phase equilibria in the K2SO4–Rb2SO4–H2SO4–H2O system have been investigated under isothermal conditions at 25°C. The concentration limits of crystallization of solid solutions with the general formulas (KxRb1–x)2SO4, (KxRb1–x)3H(SO4)2, (KxRb1–x)9H7(SO4)8 ⋅ H2O, and KxRb1–xHSO4 and the K0.55Rb0.45HSO4 phases are determined. The dependences of the equilibria of saturated solutions on the initial production conditions are revealed. The growth conditions for large single crystals of complex acid potassium–rubidium sulfates are determined. The phase-equilibrium diagram of the system is constructed.