Measurements of the Solid–Liquid Equilibria in the Quaternary System NaCl–NaBr–Na2SO4–H2O at 323 K

Phase equilibria of the quaternary NaCl–NaBr–Na₂SO₄–H₂O system at 323 K were studied by the isothermal dissolution equilibrium method. The solubilities of salts and densities of saturated solutions were determined. Solid solutions [Na(Cl, Br)] were found in the experiments. The phase diagram of the quaternary system has no invariant point, but has one univariant curve at the boundary of Na(Cl, Br) and Na₂SO₄ crystallization fields. The experimental results show that an increase of the NaBr concentration is accompanied by an obvious increase of the solution density and the decrease of the solubilities of NaCl and Na₂SO₄.     

Phase Equilibria in the System NH4Al(SO4)2–H2SO4–H2O

Equilibrium solubility curves of the ammonium aluminium sulphate in aqueous solutions of sulphuric acid have been calculated using checked literature data and our own measurements. The concentration of sulphuric acid ranged from 0 to 23 mass%, temperature range between 20 and 60°C has been extrapolated up to 75°C by means of a thermodynamically based correlation method. The solubility correlation as well as the hydration analysis implied a possible destructuralization of solutions at higher acid concentrations. This revised version was published online in August 2006 with corrections to the Cover Date.     

25 ℃下Na+, K+, Mg2+//Cl-, SO2-4, NO-3, H2O体系液固相平衡

本文应用等温溶解平衡法,研究了Na+, K+, Mg2+//Cl-, SO42-, NO3-, H2O六元体系在25℃、氯化钠饱和时的相平衡关系,测定了溶解度数据,并绘制出相应的相图. 研究表明： 25℃时,该体系在氯化钠饱和的区域里存在8种复盐,有15个两盐结晶区,25个零变量点;零变量点中只有一个共结点,为Mg(NO3)2?6H2O、NaCl、MgCl2?6H2O、MgSO4?(1～6)H2O、KCl?MgCl2?6H2O五盐共饱点,其余为反应点. 在此基础上,研究了新疆硝酸盐卤水矿蒸发析盐规律.     

Pitzer Parameters for the Pertechnetate Ion in the System Na+/K+/Mg2+/Ca2+/Cl−/SO 2 4 −/TcO − 4 /H2O at 25°C

Isopiestic vapor pressure experiments are performed at 25°C with aqueous Mg(TcO₄)₂ solutions and with ternary mixtures containing various combinations of NaTcO₄, Mg(TcO₄)₂, NaCl, MgCl₂, Na₂SO₄, and MgSO₄. The osmotic coefficients of the binary solutions are used to evaluate the binary Pitzer parameters ⁽⁰⁾, ⁽¹⁾, and C for Mg(TcO₄)₂. We previously reported these parameters for NaTcO₄. The binary parameters for KTcO₄ and Ca(TcO₄)₂ are evaluated from solubilities of KTcO₄ in KCl and CaCl₂ solutions, respectively. The mixing parameters _{TcO 4} ^– _/Cl ^–, _{M/TcO 4} ^– _/Cl ^–, _{TcO 4} ^– _{/SO 4} ^2– , _{M/TcO 4} ^– _{/SO 4} ^2– , and _Na ⁺ _/Mg ²⁺ _/TcO4 ^2– are calculated from either osmotic coefficients or solubilities in the corresponding ternary mixtures. The evaluated set of Pitzer parameters predicts well the activity coefficients and solubilities of KTcO₄ in multicomponent systems.     

Solid-liquid Metastable Equilibria in Quaternary System （NaCl＋Na2CO3＋Na2SO4＋H2O） at 273.15 K

The metastable phase equilibria of the quaternary system NaCl+Na2CO3+Na2SO4+H2O were studied at 273.15 K. The salts' solubilities, densities and pH values of the equilibrated solution in this system were determined. According to the experimental data, the metastable equilibrium phase diagram, the diagram of density vs. composition and pH vs. composition diagram were plotted. The phase diagram consists of five univariant curves, four crystallization fields and two invariant points. The four crystallization fields correspond to sodium carbonate decahydrate (Na2CO3·10H2O), sodium sulfate decahydrate(Na2SO4·10H2O), sodium chloride(NaCl) and burkeite(2Na2SO4· Na2CO3), respectively. The crystallization field of sodium sulfate decahydrate(Na2SO4·10H2O) is the largest, which indicates that sodium sulfate is easy to saturate and crystallize from solution at 273.15 K.     

Solubility and Crystallization in the System MgCl2–MgSO4–H2O at 50 and 75°C

The system MgCl₂–MgSO₄–H₂O has been investigated experimentally and modeled thermodynamically according to the Pitzer method at 50 and 75°C. It was found that, even when seemingly all requirements for reaching the stable thermodynamic equilibrium are fulfilled, the crystallization of higher hydrates as metastable phases is possible, and cannot be avoided in each crystallization field of a stable lower hydrate of magnesium sulfate. Crystallization of MgSO₄ · x H₂O (x = 1, 4, 6) and MgCl₂ · 6 H₂O at 50°C and of MgSO₄ · H₂O and MgCl₂ · 6 H₂O at 75°C as stable phases has been observed. Three metastable crystallization fields of MgSO₄ · x H₂O (x = 4, 6, 7) have been detected at 50°C and two of MgSO₄ · x H₂O (x = 4, 6) at 75°C. The results obtained and the contradictions existing in the literature with respect to the solubility and the crystallizing solid phases are discussed in terms of the crystal structures.     

Solid–Liquid Stable Equilibrium of the Quaternary System LiCl + NaCl + Li2SO4 + Na2SO4 + H2O at 288.15 K

Journal of Solution Chemistry - In this study, the isothermal saturation method was applied to obtain the data for solid–liquid equilibria in a system consisting of four solids...     

Solubilities in the Na,Ca‖SO4,F-H2O system at 0°C

Solubilities at invariant points of the Na,Ca‖SO₄,F-H₂O system at 0°C was studied, and a phase diagram of this system at 0°C was constructed.     

Experimental Study on Phase Equilibria in Na2B4O7–Na2SO4–H2O and Li2B4O7–Na2B4O7–H2O Aqueous Ternary Systems at 273 K

Russian Journal of Physical Chemistry A - The solubility data for ternary systems Na2SO4–Na2B4O7–H2O and Li2B4O7–Na2B4O7–H2O at 273 K were obtained experimentally by the...     

Solid-liquid Equilibria in the Quaternary System Na＋, K＋//Br-, B4O72--H2O at 298 K

According to the compositions of the underground gasfield brines in the west of Sichuan Basin, the solu- bilities and densities of the solid-liquid equilibria in the quaternary system Na＋, K＋//Br-, B4O72--H2O at 298 K were determined by the method of isothermal solution saturation. From the experimental data, the phase diagram, water content diagram and density-composition diagram were obtained. This quaternary system is of simple eutectic type, without double salt and solid solution. There are two invariant points, five univariant curves, four fields of crystalli- zation in the system. The equilibrium solid phases are Na2BaO7·10H20, K2B4O7·4H2O, NaBr·2H2O and KBr. Na2B4O7·10H2O has a larger crystallization field, and NaBr·2H2O has a smaller crystallization field. It is also found that bromide has the salting-out effect on borate in the quaternary system Na＋, K＋//Br-, B4O72--H2Oat 298 K.     

Prediction of phase equilibrium for the aqueous systems Rb+, Cs+/Cl−, SO 4 – -H2O and K+, Cs+/Cl−, SO 4 2− -H2O at 25°C

The Pitzer ion-interaction extended by Harvic and Weare was applied to predict the solubility isotherms of reciprocal quaternary systems in which mixed crystals are formed. On the basis of data concerning the binary and ternary subsystems, the four components systems Rb⁺, Cs⁺/Cl^?, SO ₄ ^2? -H₂O, and K⁺, Cs⁺/Cl^?, SO ₄ ^2? -H₂O were investigated at 25°C.The results of calculation can be used to model salt crystallization during the concentration of brines.     

Phase Equilibria in the Ag–In–Pd System at 700°C

Summary. Phase equilibria in the Ag–In–Pd system were determined at 700°C based on experimental results for 21 alloys. A ternary compound T₁ (with the approximate composition AgInPd₂) was identified by XRD analysis. These data were compared with the results of a CALPHAD-type prediction, based on binary thermodynamic data only and a symmetrical Redlich–Kister–Muggianu model. The experimental results will serve as a basis for refined thermodynamic modeling of the different phases in this ternary system.     

Phase Equilibria in the Ni–Al–W System at 900°C

Summary. Multicomponent Ni-base alloys exhibit good mechanical properties even at elevated temperatures and they are widely used for industrial production of exertion-resistive parts of engines. These properties are mainly determined by the coexistence of a disordered γ matrix with a face centred cubic lattice and cuboidal domains of its ordered γ′ structure. Therefore it is useful to study phase equilibria in Ni-base systems, namely in the regions involving both mentioned phases. One of the conclusions of our recent work on Ni–Al–Cr–W system was a necessity of modification of selected thermodynamic parameters of the ternary Ni–Al–W subsystem in order to achieve a better agreement of our experimental observations with theoretical modelling. This involves new measurements of the microstructure of selected samples of the Ni–Al–W system at 900°C and the comparison of the results with existing literature data in order to confirm our conclusions on higher order system investigated before. It is a first step on the way to an assessment of the Ni–Al–W system, which has not been done before.     

Phase equilibria of the Na,K,Mg,Ca//SO4,Cl-H2O system at 50°C in the crystallization range of glaserite 3K2SO4·Na2SO4

Phase equilibria of the Na,K,Mg,Na,K,Mg,Ca//SO₄,Cl-H₂O system are studied at 50°C via translation in the crystallization range of glaserite (3K₂SO₄ · Na₂SO₄). It is found that glaserite as the equilibrium phase of the investigated system at 50°C participates in the formation of 21 invariant points, 21 monovariant curves, and 34 divariant fields. A fragment of the phase equilibria diagram of the investigated system is constructed in the crystallization range of glaserite.     

Phase equilibria in the Na,K,Mg,Ca‖SO4,Cl-H2O system at 50°C in the halite crystallization field

Phase equilibria of the Na,K,Mg,Ca‖SO₄,Cl-H₂O system at 50°C in the halite (NaCl) crystallization field were studied using the translation method. Halite, which is an equilibrium phase of the title system at 50°C, was found to be involved in 25 invariant points, 59 monovariant curves, and 43 divariant fields. A fragment of the equilibrium phase diagram of the title system in the halite crystallization field was constructed.     

Phase equilibria in the Na,K,Mg,Ca‖SO4,Cl-H2O system at 50°C in the astrakhanite crystallization region

Phase equilibria of the Na,K,Mg,Ca‖SO₄,Cl-H₂O system at 50°C in the astrakhanite (Na₂SO₄ · MgSO₄ · 4H₂O) crystallization region were studied using the translation method. Astrakhanite was found to be involved, as an equilibrium phase of the title system, in 35 divariant fields, 39 monovariant curves, and 22 invariant points. The data gained were used to construct a fragment of a schematic equilibrium phase diagram of the title system in the astrakhanite crystallization region.     

Phase equilibria in the Na,Ca‖SO4,CO3,F-H2O at 0°C

Phase equilibria in the Na,Ca‖SO₄,CO₃,F-H₂O system at 0°C were studied using the translation method. Seven invariant points, 18 monovariant curves, and 17 divariant fields were found to exist. A looped phase diagram (phase complex) of the title system was constructed.