Phase Equilibria and Phase Diagrams of the Li+, Na+//Cl–, CO32––H2O System at 323.15 and 348.15 K

The solubility equilibrium of Li+, Na+//Cl–, CO32– −H2O quaternary systems at 323.15 K and 348.15 K was studied via the isothermal solubility equilibrium method, and the complete phase diagrams were obtained including the properties of liquid density and pH. Solid species of LiCl·H2O, Li2CO3, NaCl, and Na2CO3·H2O are found in the quaternary system at 323.15 K and 348.15 K, and one double salt of Li2CO3·Na2CO3 is found at 348.15 K. The liquid phase of two invariant points and five univariant curves at 323.15 and three invariant points and seven univariant curves at 348.15 K in the quaternary system is determined. Li2CO3 covers the largest solid phase region and is hardly influenced by temperature; Li2CO3–NaCl is a stable salt pair, and its cosaturated solubility is the least at the diagonal line of Li2CO3–NaCl.