Equilibrium Liquid Phase Analysis And Phase Diagram Of The Quinary System K⁺,Rb⁺,Mg²⁺//Cl^-,borate-H₂O At 298K

The equilibrium liquid phase analysis and phase equilibria of the quinary system K⁺, Rb⁺, Mg²⁺ // Cl^-, borate- H₂ O and the quaternary subsystem K⁺, Mg²⁺ // Cl^-, borate-H₂ O, K⁺, Rb⁺ // Cl^-, borate- H₂ O, and Rb⁺, Mg²⁺ // Cl^-, borate- H₂ O were studied at T = 298 K using an isothermal dissolution method. The density, refractive index and solubility of the equilibrated solution were determined. Based on the experimental data, the space phase diagram, the projected diagram, and the diagrams of the density vs composition, refractive indices vs composition of this quaternary system at 298 K were constructed.In order to ensure the accuracy of equilibrium liquid phase analysis, analysis of each kind of ion method has been carried on the evaluation of uncertainty. Under the condition of selected samples by the analysis uncertainty, finally get the 95 % ethylene diamine tetraacetic acid titration under the confidence probability of magnesium ions content is C(Mg²⁺) = 0.0500±0.0007 mol/L; Chlorine ion determined with silver nitrate method is C?Cl^-? = 2.0000 ± 0.0256 mol/L; sodium tetraphenylborate?STPB?-hexadecyl trimethy lammonium bromide?CTAB? back-titration of potassium content is C?K⁺? = 0.0250 ± 0.0006 mol/L; volumetric method of borate content is C?B4O72-? = 0.0400 ± 0.0009 mol/L; By ICP-OES and engage method of rubidium ions content is C?Rb⁺? = 0.1000 ± 0.0005 mol/L. The results show that ion analysis method is accurate and reliable.The phase equilibria of the quaternary system K⁺, Mg²⁺ // Cl^-, borate- H₂ O at 298 K consists of three invariant points, seven univariant curves and five crystallization fields corresponding to single salt Mg B4O7·9H₂O, KCl, Mg Cl2·6H₂O,K2B4O7·4H₂O and double salt KCl·Mg Cl2·6H₂O. The largest crystallization fields is Mg B4O7·9H₂O, the smallest crystallization fields is Mg Cl2· 6H₂ O, the results show that the solubility of Mg Cl2·6H₂O is the largest, the solubility of Mg B4O7·9H₂O is smallest. Comparisons among the stable phase diagrams of system K⁺, Mg²⁺ // Cl^-, borate-H₂ O at 288 K, 298 K and 323 K show that the crystalline forms of salts are the same, and the crystalline form of borate is B4O5?OH?42-, whereas the crystallization region of K2B4O7· 4H₂ O increased with the rise of temperature, and the crystallization region salt Mg B4O7 · 9H₂ O is decreased.The phase equilibria of the quaternary system K⁺, Rb⁺ // Cl^-, borate- H₂ O at 298 K is of a complex system, consists of three invariant points, seven univariant curves and five crystallization fields corresponding to single salt Rb B5O8·4H₂O, KCl, Rb Cl, K2B4O7·4H₂O and solid solution?K, Rb? Cl. The largest crystallization field is Rb B5O8·4H₂O, the smallest crystallization fields is Rb Cl. Comparisons between the stable phase diagrams of the system K⁺, Rb⁺// Cl^-, borate- H₂ O at 298 K and 323 K show that the crystalline form of salts are not change, while the crystallization region change slightly the change of temperature.The phase equilibria of the quaternary system Rb⁺, Mg²⁺ // Cl^-, borate- H₂ O at 298 K is of a complex system, its phase diagram consists of three invariant points, seven univariant curves and five crystallization fields corresponding to single salt Mg B4O7·9H₂O, Rb B5O8·4H₂O, Mg Cl2·6H₂O, Rb Cl, double salt Rb Cl·Mg Cl2·6H₂O. Comparisons among the stable phase diagrams of system Rb⁺, Mg²⁺ // Cl^-, borate-H₂ O at 298 K, 323 K and 348 K show that the crystalline form of salts are the same, whereas the crystallization region of Rb B5O8·4H₂O increased and that of salt Mg B4O7·9H₂O is decreased with the increase of temperature,.The space diagram of the quinary system K⁺, Rb⁺, Mg²⁺ // Cl^-, borate- H₂ O at 298 K is composed of seven invariant points, twenty-one univariant curves and nine crystallization zones. This system is of a complex type with the appearance of double salt KCl·Mg Cl2·6H₂O, Rb Cl·Mg Cl2·6H₂O and solid solution?K, Rb?Cl. The projected phase diagram saturated with salt KCl consists of two invariant points, five univariant curves and four crystallization fields. The largest crystallization field is?K, Rb? Cl, and the smallest crystallization field is KCl·Mg Cl2·6H₂O. The projected phase diagram saturated with salt Rb2B4O7 consists of four invariant points, nine univariant curves and six crystallization areas. The largest crystallization field is Mg B4O7·9H₂O, and the smallest crystallization field is Mg Cl2·6H₂O.