Study on phase diagrams and properties of solutions in ternary systems Li~+,K~+(Mg~(2+))/SO_4~(2-)-H_2O at 25℃

摘要

Solubilities of ternary systems Li~+,K~+/SO_4~(2-)-H_2O (1) and Li~+,Mg~(2+)/SO_4~(2-)- H_2O (2) were investigated by isothermal method at 25℃. Physico-chemical properties of solutions, such as density, refractive index, viscosity, conductivity and pH, were determined. Phase diagram of the system (1) consists of three solubility branches and three crystallization fields corresponding to K_2SO_4, Li_2SO_4·H_2O and LiKSO_4. LiKSO_4 is an incongruent compound, and its transition point is estimated graphically to be 45.5—46.0℃. No solid solution of LiKSO_4 with Li_2SO_4·H_2O was found in the system. The system (2) is a simple eutonic type. Pitzer model of electrolyte solution was used to check the obtained solubilities. Data comparison gives good agreement. Two equations were used to correlate density, refractive index of the solution with its composition. Differences between measured and calculated values are less than 0.6% for density, 0.15% for the latter.