K2SO4-K2HPO4-H2O phase diagram in the region of heterogeneous supercritical fluids

Our experimental study of phase equilibria in the K 2 SO 4 -K 2 HPO 4 -H 2 O system at temperatures up to 500°C and pressures up to 100 MPa was directed to determine the sequence of phase transformations that generate heterogeneous supercritical fluids whose existence region propagates from the K 2 SO 4 -K 2 HPO 4 -H 2 O subsystem into the ternary system. We found that supercritical fluids become heterogeneous as a result of addition of K 2 HPO 4 starting with l 1 - l 2 critical phenomena in saturated solutions, with the attendant amalgamation of the stable immiscibility region that propagates from the K 2 HPO 4 -H 2 O system and the metastable liquid-liquid phase separation that originates from the K 2 SO 4 -H 2 O system. Our experimental results and the topological analysis of phase equilibria in the vicinity of the critical point of water gave us the full scenario of the phase behavior of the title ternary system in the region of the subcritical and supercritical parameters of state.