Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

To understand the crystallographic forms of salts in sulfate systems containing sodium and rubidium (cesium), the stable phase equilibria of ternary systems Na2SO4 + Rb2SO4 + H2O and Na2SO4 + Cs2SO4 + H2O at 298.2 K were studied with the isothermal dissolution method. The composition and crystallographic forms of the equilibrated solid phase was verified by Schreinemaker's wet residue method combined with X-ray diffraction. Experimental results show that there is no double salt or solid solution fromed. The stable phase diagram of Na2SO4 + Rb2SO4 + H2O at 298.2 K is characterized by one invariant point(H), two univariant curves and two crystallographic forms(corresponding to Na2SO4*10H2O and Rb2SO4). The ternary system Na2SO4 + Cs2SO4 + H2O is of the hydrate type II, there are two invariant points(E1, E2), three univariant curves and three crystallographic forms(corresponding to salts Na2SO4*10H2O, Na2SO4 and Cs2SO4). Affected by the unique structure of Cs+, both salt Na2SO4*10H2O and Na2SO4 have been found in Na2SO4 + Cs2SO4 + H2O system at 298.2 K. Furthermore, the density and refractive index of the equilibrated solution have the analogous variation tendency and regularly change with the change of concentration.