Densities and Apparent Molar Volumes of Aqueous Solutions of Li2SO4 and LiCF3SO3 at Temperatures from 293 to 343 K

Densities of aqueous solutions of lithium sulfate (Li2SO4) and lithium trifluoromethanesulfonate (LiCF3SO3) at solute molalities ranging from 0.05 to 2.7 or 9.6 mol.kg(-1), respectively, have been measured by vibrating-tube densimetry over the temperature range 293.15 <= T/K <= 343.15 at 0.1 MPa pressure. The apparent molar volumes (V-phi) of Li2SO4(aq) and LiCF3SO3(aq) derived from these data were fitted using an extended Redlich-Rosenfeld-Meyer equation. The V-phi values for the two systems exhibit quite different dependences on concentration and temperature, as do the isobaric expansibilities. A combination of the present and literature data reveals that the densities for Li2SO4(aq) given in o standard compilations are unreliable at low concentrations. Comparison of the present results with literature data for related salts shows that V-phi(LinX) and V-phi(NanX) exhibit a crossover at approximate to 0.5 mol.kg(-1) for both systems, similar to those observed previously for other lithium and sodium salts. Consideration of an appropriate series of lithium salts suggests that anion size influences departures from the Debye-Huckel limiting law for volumes, whereas for a series of sulfate salts cation size does not appear to be a major factor.