Activity Coefficients of Electrolytes from Liquid Membrane Cells. XII. Magnesium, Lanthanum, and Tris(ethylenediamine)cobalt(III) Salts of the 1,5-Naphthalenedisulfonate Anion at 298.15 K

摘要

Activity coefficients of the highly charged electrolytes Mgds, La₂ds₃, and [Co(en)₃]₂ds₃ (en = ethylenediamine, ds2−=1,5-naphthalenedisulfonate anion), were determined at 298.15 K using liquid-membrane cells. These salts are found not to display large negative deviations from the Debye-Hückel limiting slope in the dilute regions, which characterize the corresponding sulfate salts. Theoretical calculations based on the primitive model (charged hard spheres in an unstructured dielectric medium) reproduce the behavior of these salts correctly up to concentrations of 0.01 mol⋅kg−1 or more (0.1 mol⋅kg−1 for Mgds), although ds2−, far from resembling a charged sphere, is a planar ion with charges distant from one another. The Pitzer model parameter values are reported for the activity and osmotic coefficients.