In this paper, the phase equilibria of the Li+, Na+, Rb+ //Cl- ? H2O with quaternary lithium rubidium chloride system at 298.2 K was studied by isothermal evaporation method, and the solubilities, densities and refractive indices of the equilibrated solution were determined experimentally. On the basis of the measured data, the stereo phase diagram, the dry-salt phase diagram, the density vs composition diagram and the refractive index versus composition diagram were constructed. Results show that the quaternary metastable phase diagram at 298.2 K consists of one invariant point, three univariant curves, and three crystallization fields corresponding to single salts potassium chloride (NaCl), rubidium chloride (RbCl), lithium chloride monohydrate (LiCl·H2O). the phase diagrams of the quaternary system Li+, Na+, Rb+ // Cl- - H2O and Li+, K+, Rb+ // Cl- - H2O at 298.2 K were compared and analyzed, and the effects of Na+ and K+ in the three system Li+, Rb+ // Cl- ? H2O were summarized. Using the empirical formula of refractive index calculation to the theoretical value of refractive index, the maximum absolute error between the calculated and experimental data is less than -0.0090, which proves the reliability of the experimental data.
