To exploit the valuable features of brine resources with high concentrations of borate ions, the solubility data and corresponding physicochemical properties (refractive index, density, viscosity, and pH) for the reciprocal quaternary system (Na + , Ca 2+ //Cl − , borate−H 2 O) at 288.15 K were determined experimentally using the method of isothermal dissolution equilibrium. The dry-salt and water-phase diagrams and the diagrams of physicochemical properties (refractive index, density, viscosity, and pH) against J(B 4 O 7 2− ) in the solution were established. In the dry-salt phase diagram of the quaternary system at 288.15 K, two invariant points, five univariant curves, and four crystallization regions corresponding to gowerite (CaB 6 O 10, and sodium chloride (NaCl) were found. The area of crystallization region of CaB 6 O 10 •5H 2 O is larger than that of other coexisting salts, which indicates that the solubility of gowerite in this system is the lowest and that it is more easily separated by crystallization; the areas of crystallization regions of Na 2 B 4 O 7 • 10H 2 O, NaCl, and CaCl 2 •6H 2 O are decreased in turn. In this system, there are no double salts or solid solutions experimentally found. The water-phase diagram of the system indicates regular variation of J(H 2 O) on J(B 4 O 7 2− ), and the physicochemical properties of the quaternary system varied regularly with increasing Janecke index values of J(B 4 O 7 2− ).

The solid−liquid phase diagram of salt−water systems containing lithium, calcium, and borate is of significance to understand the thermodynamic properties of the electrolytes and promote the productions of lithium and calcium borates. Solubilities and physicochemical properties including density and refractive index of the quinary system (Li + , Na + , Ca 2+ //Cl − , borate−H 2 O) at 288.15 K and 0.1 MPa were investigated by the isothermal dissolution equilibrium method for the first time in this work. The dry-salt, the water-phase, and the sodium-phase diagrams were plotted. In the dry-salt diagram, there are four invariant points, nine isothermal univariant curves, and six crystallization regions (all saturated with NaCl), and no solid solution was found in the system. With a view of the crystallization region, the areas of crystallization regions of minerals are in the order of Nanamely, the solubility of borax is the lowest and could be the first crystallized-out mineral with halite. Corresponding physicochemical properties including density and refractive index of the quinary system at 288.15 K were regularly changed with the Janecke index of calcium J(Ca 2+ ) in the solution.

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