Solubility prediction for the HCl–MgCl2–H2O system at 40 C and solubility equilibrium constant calculation for HCl ⋅ MgCl2 ⋅ 7H2O at 40 C

The component solubilities of the HCl–MgCl₂–H₂O system at 40 ^°C were calculated by using Pitzer’s ion-interaction model and the solubility equilibrium constant of HCl⋅MgCl₂⋅7H₂O at 40 ^°C was evaluated according to the solubility data for the HCl–MgCl₂–H₂O system at −19.8, 0, 20, 25 and 50 ^°C. This study can provide the parameters necessary for solubility prediction for the HCl–LiCl–MgCl₂–H₂O system at 40 ^°C and supply a theoretical basis for the manufacturing process which was proposed by Gao and employed to extract MgCl₂⋅6H₂O from salt lake brine.     

Solubility prediction for the nonelectrolyte urea–hydrogen peroxide–water system and thermodynamic solubility product calculation for CO(NH2)2 ⋅ H2O2 using the modified Pitzer model

The Pitzer interaction model, which has been applied successfully to the thermodynamic simulation of electrolyte solutions and electrolyte–nonelectrolyte solutions, was extended to nonelectrolyte–nonelectrolyte solution system. In the present work, the modified Pitzer model was used for calculation and correlation of the ternary CO(NH₂)₂–H₂O₂–H₂O system at 283.15 K. The value of the Pitzer interaction parameters for the ternary system and the thermodynamic solubility product of CO(NH₂)₂⋅H₂O₂ were determined using a least-square optimization procedure with coupling activity coefficient and solubility data. The predicted isothermal solubilities agree well with the result obtained from the experiment. The results indicated that the modified Pitzer model could be successfully used to predict the component solubility of the nonelectrolyte–nonelectrolyte system.     

Liquid–solid equilibria in quinary system Na,Mg/Cl,SO4,NO3–H2O at 298.15 K

In order to develop the nitrate deposits found close to Lop Nur in the Xinjiang region in China, the solubilities of the system Na⁺,Mg²⁺/Cl⁻,SO₄²⁻, NO₃⁻–H₂O and its subsystems, the quaternary systems Na⁺,Mg²⁺/SO₄²⁻,NO₃⁻–H₂O and Mg²⁺/Cl⁻,SO₄²⁻,NO₃⁻–H₂O, were studied at 298.15 K. The phase diagrams were plotted according to the solubilities achieved. In the equilibrium phase diagram of Mg²⁺/Cl⁻,SO₄²⁻,NO₃⁻–H₂O, there are two invariant points, five univariant curves and four regions of crystallization: Mg(NO₃)₂6H₂O,MgCl₂6H₂O,MgSO₄7H₂O and MgSO₄(1–6)H₂O. In the equilibrium phase diagram of Na⁺,Mg²⁺/SO₄²⁻, NO₃⁻–H₂O, there are five invariant points, eleven univariant curves and seven regions of crystallization: Na₂SO₄,Na₂SO₄10H₂O,NaNO₃,MgSO₄Na₂SO₄4H₂O,NaNO₃Na₂SO₄2H₂O,Mg(NO₃)₂6H₂O and MgSO₄7H₂O. In the equilibrium phase diagram of the Na⁺, Mg²⁺/Cl⁻,SO₄²⁻,NO₃⁻–H₂O system, there are six invariant points, and ten regions of crystallization: NaCl, NaNO₃,Na₂SO₄,Na₂SO₄10H₂O,MgSO₄Na₂SO₄4H₂O, NaNO₃Na₂SO₄2H₂O,MgCl₂6H₂O,Mg(NO₃)₂6H₂O, MgSO₄(1–6)H₂O and MgSO₄7H₂O.     

Correlation of solubilities for the system with the Pitzer model at 15, 25, 50, and

Solubility data of the NaCl+LiCl+H₂O system have been measured at 15 C. These data along with others recorded in the literature, at 25, 50, and 100 C, have been correlated using the Pitzer model and the extended Debye–Hückel model. The latter was used to determine the activity and osmotic coefficients of the binary systems NaCl+H₂O and LiCl+H₂O. The results obtained in this work show that the calculated solubility values are in good agreement with the experimental ones.     

Water activities, osmotic and activity coefficients of the system (NH4)2SO4–K2SO4–H2O at the temperature 298.15 K

The mixed aqueous electrolyte system consisting of ammonium and potassium sulfates has been studied using the hygrometric method at the temperature 298.15 K. The water activities are measured at total ionic strength values ranging from 0.60 to 8.25 mol kg⁻¹ for different ionic strength fractions (y) of (NH₄)₂SO₄ with y=0.20, 0.50 and 0.80. The obtained data allow the deduction of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii–Stokes–Robinson (ZSR), Kusik and Meissner (KM), Robinson and Stokes (RS), Lietzke and Stoughton (LS II), Reilly–Wood and Robinson (RWR) and Pitzer models. From these measurements, the new Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture.