Mixed alkali effect in sodium thiocyanate–potassium thiocyanate – acetamide melt systems

Abstract

Electrical conductivity and molar volume of the 0.25[xNaSCN + (1 −x)KSCN] + 0.75CH3CONH2 systems were measured as functions of temperature [Formula: see text] and composition (x = 0.0 – 1.0 mol fraction). Temperature dependence of the electrical conductivity was non-Arrhenius in nature and has been analysed by using the Vogel–Tammann–Fulcher (VTF) equation. Molar volume data were fitted to an equation similar to the VTF equation based on the free volume model. Molar volumes and intrinsic volumes were found to be additive in nature. Electrical conductivity isotherms deviate from linearity in different fashion for different temperature regions. The onset of the mixed alkali effect is governed by the anion polarization effect, by a contribution of the auto-dissociated molten acetamide, and by polymeric-type solvated ions. Key words: electrical conductivity, sodium thiocyanate, potassium thiocyanate, acetamide, mixed alkali effect.