Prediction of solubilities in the quaternary system Na+, K+/Cl-, HCO3--H2O and Na+, K+/SO2-4, HCO3--H2O at 298 K

Based on the condition of dissolution equilibria of salts and the discrimination of stable invariant points, the solubilities and phase-diagrams of the two quaternary systems Na+, K+/Cl-, HCO-3-H2O and Na+, K+/SO2-4, HCO-3-H2O at 298 K were predicted by using Harvie-Weare equation (1980). Two invariant points and four regions of crystallization: NaCl, NaHCO3, KCl and KHCO3 are found in the phase diagram of the first system, and three invariant points and five regions of crystallization: Na2SO4 &middot 10H2O, K3Na (SO4)2, K2SO4, NaHCO3 and KHCO3 in that of the second system. Consistent with the solubilities of the ternary subsystems in the literature, the results are of practical significance in studying the formation and evolution of the salt deposit in alkaline salt lakes and designing salt chemical production.