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

This thesis includes a review and a research section. In the review, the basic knowledge of rubidium, cesium and their compounds is introduced firstly. Then we present the investigation of inorganic salts-mixed solvent systems and the importance is paid on the systems of alkali metal and alkali earth metal salts. The equilibrium solubility and physico-chemical properties of these systems can provide not only basic thermodynamic data for solution chemistry, but also new purification methods for inorganic salts.The research section contains ten subunits. In the research section, we have used a semimicro installation to study phase diagrams of Cs2SO4/Cs2CO3 -ROH( R=CH3-, C2H5-, n-C3H7- and i-C3H7-) -H2O ternary systems at ( 0, 10, 20. 25, 30, 40 and 50) ℃ and CsNO3-C2H5OH-H2O system at (-10, 10, 30and 50) ℃ In the Cs2SO4-CH3OH-H2O, Cs2CO3-CH3OH-H2O and CsNO3 -C2H5OH-H2O systems, the solution did not appear two phases and only a solubility limit is observed. The exsistence of CH3OH and C2HsOH significantly decreases the solubility of cesium salts in water. But the solution of other systems has appeared two phases, organic (light) phase and water (heavy) phase. With the increasement of temperature and the number of the carbon atoms in the chain of the aliphatic alcohol, the two-phase area increased. Samples of the equilibrium solid phase in Cs2SO4 - ROH - H2O systems analyzed by TGA showed that it consisted of anhydrous salt. Five zones are observed in the complete phase diagram. They are L, L+L, L+S (two ) and L+L+S, respectively. There are two kinds of equilibrium solids in Cs2CO3 - ROH - H2O systems, one is anhydrous salt and the other is Cs2CO3-3.5H2O. So there are six zones in the phase diagram. They are L, L+L, L+S(two), L+L+S and L+S+S, respectively.We have also studied the equilibrium solubility of the Cs2SO4 -PEG(poly(ethylene glycol)) - H2O system at (25, 35 and 45)℃. Two liquid phases appeared in the solution, and with the increasement of temperature and the molecular weight of PEG, the two-phase area increased. Six zones are observed in the phase diagrams. In the L+S+S zone, one solid is CS2SO4, and the other is PEG.The experimental data of all binodal curves were given using afive-parameter equation, y = a + bx0.5 +cx + dx2+ex3 Tie lines were correlated by the Othmer-Tobias and Bancroft's equations. The density and refractive index for liquid phases have also been determined and the mechanism about the formation of two liquid phases in such ternary system has been suggested.