Phase Equilibria for the Reciprocal Aqueous Quaternary System Li+, Rb+//Cl−, Borate–H2O at 323.2 K

The isothermal dissolution equilibrium method was applied for the solid–liquid equilibria experiments of the reciprocal aqueous quaternary system Li+, Rb+//Cl−, borate–H2O at 323.2 K, and the relevant diagrams (phase diagram, water content diagram, density/refractive index against composition diagram) were plotted. It was found that there are two commensurate type quaternary invariant points with three-salt cosaturated, five univariant curves, and four crystallization fields corresponding to four single salts, rubidium chloride (RbCl), lithium chloride monohydrate (LiCl·H2O), lithium tetraborate trihydrate (Li2B4O7·3H2O), and rubidium pentaborate tetrahydrate (RbB5O8·4H2O), respectively. LiCl·H2O has a salting out effect on other coexisting salts and the size of the LiCl·H2O crystallization field is the smallest. Li2B4O7·3H2O has the largest crystallization field, which demonstrates that Li2B4O7·3H2O can be more easily separated from the solutions.