The molar conductivities of Et4NBr, n-Pr4NBr, n-Bu4NBr, and n-Bu4NBPh4 have been measured in N,N-dimethylformamide–methyl ethyl ketone (DMF–MEK) mixtures (34.5≥D≥20.10) over the maximum concentration range (2×D3×10−7 mol dm−3) along with the densities and viscosities of the solvent mixtures at 25 °C. The conductance data have been analyzed by using the Fuoss-1978 (F78) conductance equation and the results compared with those obtained from the Justice (J) and the Fuoss-Onsager-Skinner (FOS) equations. The molar conductivities at infinite dilution (Λ0), the thermodynamic association constant (KA) and the distance or the ion-size parameter (R or a°) are evaluated from these data. A better fit of the parameters was provided by the F78 equation which yielded KA and R values. The Λ0 and the KA values are found to increase with decrease in the dielectric constant of the medium and in a given solvent mixture they follow the order Et4NBr>n-Pr4NBr>n-Bu4NBr>n-Bu4NBPh4.

AIJAZ AHMAD ANSARI and M. R. ISLAM. Can. J. Chem. 66, 1223Chem. 66, (1988. The molar conductivities of Pr4NBr, Bu4NBr, Pr4NI, and Bu4NI have been measured in tert-butanol-water (t-BuOH-H20) mixtures (61.30 2 D 2 16.50) over the maximum concentration range (2 X D~ X mo1 dm-3) along with the densities and viscosities of the solvent mixtures at 25°C. The conductance data have been analysed by using the Fuoss-1978 (F78) conductance equation and the results compared with the values obtained from the Justice (J), Pitt's (P), and Fuoss-Onsager-Skinner (FOS) equations. Molar conductivities at infinite dilution (AO), the thermodynamic ion association constants (KA) and the distance or ion-size parameters (RO or a' ) are evaluated from these data. The F78 equation fitted the data better and yielded KA and R values which are in accord with the ion-association theories. The interpretation of these parameters is discussed to provide some insight on the magnitude of the ionic association and the ion-solvent interaction.