REGRESSION OF ACTIVITY COEFFICIENTS OF 1-1 TYPE POTASSIUM SALT AQUEOUS SOLUTIONS AT 25 ℃ AND OVER WHOLE CONCENTRATION RANGE

The Clegg Pitzer semi empirical thermodynamic equations were applied to the calculation of 1 1 type potassium salt aqueous solution.At 25 ℃ and over the whole concentration range,from 8 single electrolyte solutions (KF,KCl,KBr,KI,KOH,KNO 3,KClO 3,KBrO 3),the parameters W H 2O,KX ,U H 2O,KX ,and B KX were calculated,and then 8 solubility products were calculated.From 9 bi salt saturated aqueous solutions,the parameters W KXY ,U XY ,and Q H 2O,KXY were regressed,the F test was passed.

Liquid-Liquid Equilibrium for 1-Butanol-Water-KF and 1-Butanol-Water-K_2CO_3 Systems

KF or K2CO3 was added into the 1-butanol-water system and two phases were formed： water-rich phase （water phase） and 1-butanol-rich phase （1-butanol phase）. The liquid liquid equilibrium （LLE） data for 1-butanol-water-KF and 1-butanol-water-K2CO3 systems were measured at 25℃ and showed that 1-butanol phase contained negligible salt and water phase contained negligible 1-butanol when the concentrations of KF and K2CO3 in the water phase were equal to or higher than 27.11% and 31.68% , respectively. Thus water could be separated efficiently from 1-butanol-water by adding KF or K2CO3 into the system. A theoretical calculation of LLE data was calculated by using the Pitzer theory to get water activity in the water phase, and by the models, such as the Wilson, NRTL or the UNIQUAC for the 1-butanol phase. For 1-hutanol-water-KF system, the experimental data were found in good agreement with the calculated results by using Pitzer theory and Wilson equa tion, while for 1-butanol-water-K2CO3 system, the experimental data were found in good agreement with the calculated results by using Pitzer theory and UNIQUAC eauation.

Prediction of Activity Coefficients for Mixed Aqueous Electrolyte Solutions from the Data of Their Binary Solutions

The simple equation relating the activity coefficient of each solute in mixed electrolyte solution to its value in binary solutions under isopiestic equilibrium was tested by comparison with the experimental data for the 18 electrolyte solutions consisting of 1：1, 1：2, and 1：3 electrolytes. The isopiestic measurements were made on the quaternary system BaCl2-NH4Br-NaI-H2O and its ternary subsystems NaI-NH4Br-H2O, NaI-BaCl2-H2O, and NH4Br-BaCl2-H2O at 298.15K. The results were used to test the applicability of the Zdanovskii＇s rule to the mixed electrolyte solutions which contain no common ions, and the agreement is excellent. The activity coefficients of the solutes in the above quaternary and ternary systems calculated from the above-mentioned simple equation are in good agreement with the Pitzer＇s equation.

Measurements and Calculations of Solid-liquid Equilibria in Quaternary System Li2SO4-Na2SO4-K2SO4-H2O at 288 K

The isothermal dissolution equilibrium method has been used to investigate the solid and liquid equilibria of quatemary system Li2SO4-Na2SO4-K2SO4-H2O at 288 K. The phase diagram and water diagram were plotted according to the experiment results. It was found that LizSO4-Na2SO4-K2SO4-H2O quaternary system contains four double salts at 288 K. There are six invariant points, twelve univariant curves and seven areas of crystallization： Li2SO4·H2O, Na2SO4·10H2O, K2SO4,LiESO4·3Na2SO4-12H2O, Li2SO4K2SO4, Na2SO4·3K2SO4, 2Li2SO4·Na2SO4- K2SO4. Using the equilibrium solubility data of the quaternary system at 288 K, the solubility product（lnKsp） of solid phase 2LiESO4-Na2SO4.KESO4, which is not reported was acquired. Based on the chemical model of Pitzer＇s electrolyte solution theory, the solubilities for the quaternary system Li2SO4-Na2SO4-K2SO4-H2O at 288 K were calculated with corresponding parameters. Compared the results of experimental measurement with those of calculation, it was shown that the calculated values had a good agreement with the experimental ones.

Activity Coefficients of NaCI in Ethylene Glycol-Water Mixtures Using Potentiometric Measurements at 288.15, 298.15 and 308.15 K

The mean activity coefficients of NaCl in ethylene glycol-water mixtures were determined in the range of w = 0.10 to 0.40 ethylene glycol at 288.15, 298.15 and 308.15 K using potentiometric measurements. The Pitzer and extended Debye-Htickel equations were used to describe the nonideal behavior of the electrolyte. Osmotic coefficients and the standard Gibbs energy of NaCl-ethylene glycol-water were calculated.