Transport parameters of LiCl and LiBr in aqueous mixtures with organic solvents of moderate to low permittivities

Abstract

The electromotive forces (emf) E_A and E_C of the following concentration cells with transference: respectively (where X=Cl, Br), combined with the emfs E_MAX of the corresponding double cell without transference: ∣AgX∣LiX(m₂)∣Li_xHg_1-x have been measured at LiX molalities m (m₁ fixed and m₂ varied, with m₂>m₁) in 14 solvent mixtures pertaining to the three aqueous–organic solvent systems (acetonitrile+water), (1,4-dioxane+water) and (methanol+water) up to the 0.8 mass fraction of organic component. For all of the cases studied the E_Avs. E_MAX relation is a curve reaching a straight line asymptotically at low LiX molalities. The resulting ionic transference numbers t of LiX show a type of curvilinear dependence on the mass fraction of the organic component which shows analogies with that of the other alkali halides hitherto studied, but is quite distinct from that of HCl. Such a dependence is also analyzed in terms of solvation parameters and the mechanism of ionic motion, with account being taken of Stokes' law ionic radii.