Ultrasonic Studies in Electrolytic Mixtures-Complex Ion Formation

Abstract

Ultrasonic velocity and adiabatic compressibility have been studied as a function of composition for the systems: NaNO₃–Sr(NO₃)₂–H₂O; KNO₃Sr(NO₃)₂–H₂O, KCl–NaCl–H₂O; Pb(NO₃)₂–Sr(NO₃)₂–H₂O; KNO₃–Pb(NO₃)₂–H₂O, NaNO₃–Pb(NO₃)₂–H₂O; CdCl₂–KCl–H₂O; ZnCl₂–KCl–H₂O; CdBr₂–KBr–H₂O; ZnBr₂–KBr–H₂O; CdI₂–KI–H₂O; ZnI₂–KI–H₂O; CdCl₂–ZnCl₂–H₂O and CdBr₂–ZnBr₂–H₂O. The first six systems containing simple electrolytes like NaCl, KCl and NaNO₃ showed ideal behaviour i.e. linear variation of the compressibility and velocity. Solutions of cadmium halides and zinc halides in aqueous solutions of potassium halides are characterised by positive excess compressibility at a mole fraction of 0.666 of the potassium halide. This behaviour has been explained as due to the formation of complex ions of the type ZnX₄⁻⁻ and CdX₄⁻⁻.