Equilibrium Solubility And Density Of Rubidium/Cesium Salt-Mixed Solvent System And Its Phase Relationship

Rare alkali metal cesium is the positive electricity and metal that the abundant degree of nature alkali metal is minimum, the metal state is similar to rubidium and potassium. Rubidium is the limp and silvery white metal, and it is the second positive electricity and the strong alkaline element. The reaction of the rubidium is similar to that of the cesium and potassium. Studies on rare alkali mental rubidium and cesium are very few, because of their dispersion and rare. In recent years, with the development of studies on rare alkali metal rubidium and cesium, it is significant to study the separation and purification of these alkaline metals. What's more, the aim of the study of the system's phase behavior was not only to provide the plenty of basic data for the applied research but also to enrich and develop the solution chemistry.This experiment work mainly includes two sections: a review and a research.In the review, the basic knowledge of rubidium, cesium and their compounds were introduced firstly. Then we present the investigation of inorganic salts-mixed solvent systems and the importance was paid on the systems of alkali metal and alkali earth metal salts.The research section introduced the method and the results of the experiment. In the research section, we have used a semi-micro installation to study phase diagrams of C₂H₅OH-CsCl/RbCl-H₂O ternary systems at 25℃and 35℃. The C₂H₅OH-CsCl-H₂O ternary system appeared in two liquid phases: alcoholic phase and water phase, when the mass fractions of ethanol in the range of 10.37% to 49.59% at 35℃, but other solutions did not appear two phases and only a solubility limit was observed. Experimental values for density and refractive index for each ternary system and temperature, both in saturated and unsaturated solutions fit the following expression: Y=(A₀+A₁ w_salt+A₂ w_ROH+A₃ w_ROH w_salt+A₄ w_salt w_ROH²)×exp[A₅(w_ROH/w_water)+A₆(w_ROH/w_water)²] On the basis of the standard deviations, we concluded that the result could be satisfactory.At the same time, we have studied phase diagrams of ROH-RbBr-H₂O (R=CH₃-, C₂H₅-, n-C₃H₇-, i-C₃H₇-) ternary systems at (25, 35 and 45)℃, ROH-CsBr-H₂O (R=CH₃-, C₂H₅-, n-C₃H₇-, i-C₃H₇-) ternary systems at (25, 35 and 45)℃and ROH-Rb₂SO₄-H₂O(R=CH₃-, C₂H₅-, n-C₃H₇-, i-C₃H₇-) ternary systems at (25, 35 and 45)℃. In the CH₃OH/C₂H₅OH-RbBr/CsBr-H₂O ternary systems and CH₃OH/C₂H₅OH/i-C₃H₇OH-Rb₂SO₄-H₂O ternary systems, the solutions did not appear two phases and only one solubility limit was observed. It could be observed that at a fixed temperature the solubility of the salt decreased with the increasing of aliphatic alcohol, the solubility of the solution was correlated to the aliphatic alcohol content according to the four-parameter equation: ln S=A+B w₂+C w₂²+D w₂³, the result could be satisfactory. Samples of the equilibrium solid phase in the systems analyzed by TGA showed that they consisted of anhydrous salt. The "cloud point" and "tie-line" methods have been used to study the ternary system that appeared in two liquid phases, and we got the compositions of binodal curves and tie lines. In the completely phase diagram of n-C₃H₇OH-RbBr-H₂O ternary system at 25℃, five zones were observed. They are L, L+L, L+S(two) and 2L+S, respectively. The binodal curves were given by using a five-parameter equation ln w₁=A+B w₂^0.5+ C w₂+D w₂²+E w₂³. The tie lines were correlated by using the Othmer-Tobias and Bancroft equations. We also obtained the empirical constants and the standard deviation of the fit, from them we concluded that the result could be satisfactory.Second, we have studied the isothermal solubility of two quaternary systems. In the base of former ternary systems, we have performed the salt effect for the liquid-liquid region in the quaternary systems (n-C₃H₇OH-RbCl-CsCl-H₂O and n-C₃H₇OH-RbCl-Rb₂SO₄-H₂O) with the different two salts at 25℃. And we got the compositions of binodal curves and tie lines of three sectional phases. At the same time, we have studied the whole phase diagrams of the two quaternary systems at 25℃. And the data were correlated by Eisen-Joffe equations. We also made an explanation for the mechanism of liquid-liquid equilibrium.In this thesis, a series of phase equilibrium data of rubidium/cesium salt-mixed solvent systems were given out, the experimental results provided not only basic thermodynamic data for solution chemistry, but also new purification methods for inorganic salts and the partition of biomaterials.