Conductance studies of alkali iodides in mixed organic solvents I: Conductance measurements in N,N-dimethylformamide-acetonitrile mixed solvents

Limiting ionic conductivities of lithium, sodium, potassium and cesium have been obtained in pure N,N-dimethylformamide and acetonitrile and in their mixtures at 25 degrees C. The plots of the limiting ionic conductivities as a function of the mole fraction of DMF in the solvent mixtures are similar for all the ions studied and show a valley at 0.20 mole fraction of DME The conductivity and solvent viscosity data have been utilized in the modified Stokes' equation to estimate the solvation numbers of the ions in various solvent systems. For Li+, the solvation numbers range between 2.38 and 3.85; for Na+, K+ and Cs+, the solvation numbers range between 2.25 - 4.14; 1.97 - 3.10 and 1.12 - 2.23 respectively in the various solvent systems. The results of the study have been interpreted in terms of ion-solvent interactions and solvent properties.