Key words: ternary water-salts systems, supercritical phase equilibria, phase diagrams
Supercritical phase equilibria in ternary system K2SO4—KOH—H2O at 420—500 °C and up to 130 MPa pressure with binary boundary subsystems of different types are studied. The binary subsystem of type 1 do not have any critical phenomena in saturated (l = g — s) aqueous solution as well as the immiscibility equilibrium (l1—l2) (КОН—Н2O), the second binary subsystem of type 2 (K2SO4—H2O) has two critical end-points p (g = l — sK2SO4) and Q (l1 = l2—sK2SO4) with saturated aqueous solution and the liquid-liquid immiscibility equilibria. The ternary system has two three-phase equilibria (g — l — sK2SO4) and (l1 — l2 — sNa2SO4), separated by a two-phase supercritical fluid region (fl—sK2SO4) and two types of monovariant critical curves (g = l — sK2SO4) and (l1 = l2 — sK2SO4). The three?phase regions approach each other at temperature increased up to the point where the two-phase supercritical equilibrium disappeares, and the two mentioned monovariant critical curves are joined into a double homogeneous critical point (g = l — s ↔ l1 = l2 — s) at maximum temperature ∼ 445 °C and 51—52 MPa.