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

The electromotive forces (emf) E-A and E-C of the following concentration c ells with transference: Ag \AgX\LiX(m(2))\\LiX(m(1))\AgX\Ag and LixH1-x\LiX(m(1))\\LiX(m(2))\\LixHg 1-x respectively (where X = Cl, Br), combined with the emfs E-MAX of the corres ponding double cell without transference: LixHg1-x\LiX(m(1))\AgX\Ag-Ag\AgX\LiX(m(2))\LixHg1-x have been measured at LiX molalities m (m(1) fixed and m(2) varied, with m( 2) > m(1)) in 14 solvent mixtures pertaining to the three aqueous-organic s olvent systems (acetonitrile + water), (1,4-dioxane + water) and (methanol + water) up to the 0.8 mass fraction of organic component. For all of the c ases studied the E-A vs. E-MAX relation is a curve reaching a straight line asymptotically at low LiX molalities. The resulting ionic transference num bers 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 de pendence is also analyzed in terms of solvation parameters and the mechanis m of ionic motion, with account being taken of Stokes' law ionic radii.