Metastable Phase Equilibria in the Aqueous Ternary Systems KCl + MgCl₂ + H₂O and KCl + RbCl + H₂O at 323.15 K

Abstract

The metastable phase equilibria in the ternary systems KCl + MgCl 2 + H 2 O and KCl + RbCl + H 2 O were studied at 323.15 K using an isothermal evaporation method. The solubilities, densities, and refractive indices of the equilibrated solution were measured. The crystalloid forms of the solid phase were determined using chemical analysis and an X-ray diffraction method. On the basis of the experimental data, the metastable equilibrium phase diagrams and the physicochemical properties vs composition in the ternary systems at 323.15 K were plotted. In the metastable phase diagram of the ternary system KCl + MgCl 2 + H 2 O at 323.15 K, there are two invariant points, three univariant curves, and three crystallization fields, corresponding to potassium chloride (KCl), magnesium chloride hexahydrate (MgCl 2 • 6H 2 O), and a potassium and magnesium chloride double salt named carnallite (KCl • MgCl 2 • 6H 2 O). The salt KCl has the largest crystallization field and can be easily separated from the mixed aqueous solution containing potassium and magnesium chloride using an evaporation method. In the metastable phase diagram of the ternary system KCl + RbCl + H 2 O, there are two invariant points and three crystallization fields, corresponding to the single salts potassium chloride (KCl) and rubidium chloride (RbCl) and a solid solution of potassium and rubidium chloride [(K, Rb)Cl]. The crystallization field of the solid solution (K, Rb)Cl almost occupies all the phase region; thus, it is difficult to separate potassium from rubidium in chloride solution by only using evaporation and crystallization methods at 323.15 K.

Phase equilibria of AlCl3 + FeCl3 + H2O, AlCl3 + CaCl2 + H2O, and FeCl3 + CaCl2 + H2O at 298.15 K

“…There are many methods for the concentration measurement of ions in the liquid phase and wet residue, such as inductively coupled plasma (ICP), , titration, − ion chromatography (IC), and gravimetrical method . In this research, a 905 Titrando (Metrohm) was used to measure the concentrations of chlorine and calcium ions.…”

“…In this research, a 905 Titrando (Metrohm) was used to measure the concentrations of chlorine and calcium ions. The chlorine ion (Cl – ) concentration was measured by titration with silver nitrate. , The calcium ion (Ca 2+ ) concentration was determined by titration with an EDTA standard solution in the presence of alkali and a Ca-sensitive indicator. , The ferric ion (Fe 3+ ) concentration was measured by spectrophotometry (UV-2802, UNICO) . The aluminum ion (Al 3+ ) concentration was determined by EDTA complexometric titration with xylenol orange as the indicator .…”

“…The chlorine ion (Cl − ) concentration was measured by titration with silver nitrate. 20,21 The calcium ion (Ca 2+ ) concentration was determined by titration with an EDTA standard solution in the presence of alkali and a Ca-sensitive indicator. 22,23 The ferric ion (Fe 3+ ) concentration was measured by spectrophotometry (UV-2802, UNICO).…”

Solubility and Physical Properties of α-Calcium Sulfate Hemihydrate in NaCl and Glycerol Aqueous Solutions at 303.15, 323.15, and 343.15 K

“…The density (ρ) of the saturated solution was measured by a special weighing bottle method, 26 and the standard uncertainty was 0.012 g•cm −3 . The viscosity (η) was measured by an Ubbelohde capillary viscometer, and the average relative deviation of flow time was 0.02 s. All measurements were performed in a constant temperature bath monitored by a mercury thermometer with an uncertainty of ±0.05 K.…”

Thermodynamics Phase Equilibria for the Salt - Water System of Potassium and Rubidium Ions

“…Figure 1 is the metastable phase diagrams of ternary system KCl + RbCl + H 2 O at (298, 323 and 348) K (Yu et al, 2010(Yu et al, , 2011. The solid solution [(K, Rb)Cl] was formed and the crystallization region of the solid solution almost occupies all the phase region.…”