Determination of Cerium in Ceric Ammonium Sulphate by Novel Iodo-Potentiometric Method

Abstract

The basic principles of the redox reactions between cerium (Ce⁴⁺) and iodide (I^–) ions are being used to estimate quantitatively cerium in ceric ammonium sulphate by both iodometric and potentiometric methods. Precisely, the new iodo-potentiometric technique used in the present paper is a two-in-one method, wherein, both potential and volumetric data are obtained in a single process of titration at strongly acidic ceric solutions at the specified conditions. After the liberation of free iodine by adding 10 % KI to cerium solutions, the potentials (E_M) are noted. These observed potentials (E_M) have a linear relationship with molar concentration (M) of cerium solutions and again, these potentials are also found to vary linearly with iodometric titre (V₁ mL) values of standard sodium thiosulphate for different concentrations of cerium in acidic (pH 1) medium. The potential (E_M) recorded for cerium solution of unknown concentration after the addition of KI is marked in the linear plot of E_M versus V₁, mL of sodium thiosulphate and the corresponding volume (V mL) of standard sodium thiosulphate consumed for the liberated iodine is noted. From this, the amount of cerium present in ceric ammonium sulphate and its percentage is determined. The results of potentiometric titration data obtained are in excellent conformity with the obtained data from iodometric and cerimetric methods of estima-tion of cerium.