Densities of aqueous solutions of rubidium triflate (RbTf) and cesium triflate (CsTf), where Tf^– is the trifluoromethanesulfonate ion (CF₃SO₃^–), have been measured by vibrating-tube densimetry at temperatures from 293.15 to 343.15 K at 5 K intervals. Concentrations ranged from 0.03 to 5.0 mol·kg^–1 for RbTf and from 0.02 to 3.9 mol·kg^–1 for CsTf. No volumetric data for either salt appear to have been published previously. Apparent molar volumes (V_ϕ) calculated from the densities were well modeled with Pitzer equations. Standard partial molar volumes, V^o, for RbTf(aq) and CsTf(aq) were determined by extrapolation of the Pitzer fits to infinite dilution. Isobaric coefficients of thermal expansion (expansivities), α, derived from the temperature dependence of the densities, increased with concentration, especially at lower T, consistent with the solvent-structure-breaking character of their component ions. Combination of the present V^o values with a common extra-thermodynamic assumption and relevant literature data provided ionic volumes, V^o(Rb⁺,aq) and V^o(Cs⁺,aq), that show more realistic temperature dependences than previous estimates.

中文翻译：

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293.15 至 343.15 K 温度下水溶液中高浓度铷和三氟甲磺酸铯的密度和表观摩尔体积

三氟甲磺酸铷 (RbTf) 和三氟甲磺酸铯 (CsTf) 水溶液的密度，其中 Tf ^–是三氟甲磺酸根离子 (CF ₃ SO ₃ ^– )，已通过振动管密度计在 293.15 至 343.15 K 的温度和 5 K 的温度下测量间隔。RbTf的浓度范围为 0.03 至 5.0 mol·kg ^–1，CsTf 的浓度范围为 0.02 至 3.9 mol·kg ^–1。这两种盐的体积数据似乎以前都没有公布过。从密度计算的表观摩尔体积 ( V _φ ) 用 Pitzer 方程很好地建模。标准偏摩尔体积^，Vo, 对于 RbTf(aq) 和 CsTf(aq) 是通过将 Pitzer 拟合外推到无限稀释来确定的。等压热膨胀系数（膨胀率）α，源自密度的温度依赖性，随浓度增加，特别是在较低的T下，与其组分离子的溶剂结构破坏特性一致。当前的V ^o值与常见的热力学外假设和相关文献数据相结合，提供了离子体积V ^o (Rb ⁺ ,aq) 和V ^o (Cs ⁺ ,aq)，它们显示出比以前的估计更现实的温度依赖性。