Studies on Phase Equilibria of the Quaternary System LiBr–KBr–SrBr2–H2O and Ternary System LiBr–NaBr–H2O at 323 K

Stable phase equilibria of the quaternary system LiBr–KBr–SrBr2–H2O and ternary system LiBr–NaBr–H2O at 323 K were studied by an isothermal dissolution equilibrium method. The solubilities of salts in the two systems were measured experimentally. The equilibrium solid phases at invariant points in these two systems were also identified using X-ray powder diffraction and the Schreinemakers rule. According to the experimental results, the isothermal phase diagrams of the corresponding systems were drawn in detail. The experimental results show that the isothermal phase diagram of the ternary system LiBr–NaBr–H2O at 323 K has two invariant points, three univariate curves, and three single-salt solid-phase crystallization regions, corresponding to LiBr·H2O, NaBr, and NaBr·2H2O. The quaternary system LiBr–KBr–SrBr2–H2O has no double salts and solid solutions. The phase diagram of the quaternary system LiBr–KBr–SrBr2–H2O at 323 K has two invariant points, five univariate curves, and four solid-phase crystallization regions, which are LiBr·H2O, KBr, SrBr2·2H2O, and SrBr2·6H2O. The crystallization region of KBr is larger than those of LiBr·H2O, SrBr2·2H2O, and SrBr2·6H2O, which indicates that KBr has the smallest solubility and is the easiest to be precipitated from the saturated solution. In addition, a comparison of phase equilibria of some similar systems at different temperatures is presented and discussed in detail.