Isopiestic Determination of the Osmotic and Activity Coefficients of Aqueous Sodium Trifluoromethanesulfonate at 298.15 K and 323.15 K, and Representation with an Extended Ion-Interaction (Pitzer) Model

Isopiestic vapor-pressure measurements were made for aqueous sodium trifluoromethanesulfonate, NaCF 3 SO 3 (aq), using NaCl(aq) as the reference standard. The measurements for NaCF 3 SO 3 (aq) cover the molality range from 0.13643 mol·kg -1 to 5.3735 mol·kg -1 at 298.15 K and from 0.14504 mol·kg -1 to 4.3070 mol·kg -1 at 323.15 K. Values of the four parameters of an extended version of Pitzer's model for osmotic and activity coefficients, with an ionic-strength dependent third virial coefficient, were evaluated for NaCF 3 SO 3 (aq) at both temperatures, as were those of the usual three-parameter Pitzer model.