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Densities and Molar Volumes of Aqueous Solutions of Li2SO4 at Temperatures from 343 to 573 K

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journal contribution
posted on 29.08.2017, 00:00 by Lubomir Hnedkovsky, Bin Hu, Glenn Hefter
Densities of aqueous solutions of lithium sulfate (Li2SO4) at solute molalities ranging from 0.05 to 2.7 mol·kg–1 have been measured by vibrating-tube densimetry over the temperature range 373.15 ≤ T/K ≤ 573.15 at pressures close to the saturated vapor pressure of pure water. The apparent molar volumes (Vϕ) of Li2SO4(aq) calculated from these data together with previously published data at 323.15 and 343.15 K were fitted using a modified Redlich–Rosenfeld–Meyer equation, which in turn was used to extrapolate the experimental data to infinite dilution to obtain the standard partial molar volumes. A comparison of the present and literature data revealed the latter are inaccurate at low concentrations and are increasingly unreliable at higher temperatures. The combination of the present results with selected literature data produced a reliable equation of state for Li2SO4(aq) covering the temperature and pressure ranges 323.15 ≤ T/K ≤ 573.15 and 0.1 ≤ p/MPa ≤ 40. The volumetric behavior of Li2SO4(aq) was found to differ dramatically from that of Na2SO4(aq) and K2SO4(aq), especially at higher temperatures, higher concentrations, and lower pressures, reflecting the exceptional character of lithium ion hydration. Isobaric expansibilities indicated that Li2SO4(aq) remains a water structure maker over the investigated conditions.