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Iodo-potentiometric method of estimation of ceric salts in the presence of iron (Fe3+) by masking iron with fluoride (F-) ions

N.Suma, T.Jeevananda, O.G.Palanna

Iodo-potentiometricmethod, a versatile technique inwhich both iodometric and potentiometric results can be obtained in a two-in- one cell for the estimation of an oxidizing cation in analyte solution. It is observed that the Fe3+ ions present in ceric solutions can be masked completely at pH= 1.0 as FeF6 -3 by adding requisite amount of NH4HF2.Aquantitative relationship is observed between the potentials, EM, and the volumes of standard sodium thiosulphate consumed (at the end point) in potentiometric and volumetric titrations. These potentials, EM, are again found to have a linear relationship with the molar concentrations of the analyte samples taken. The titre volumes of standard sodiumthiosulphate (v1 and v2,ml) of both potentiometric and iodometric methods are identical. Interestingly, the estimation of ceric (Ce4+) is possible in the light of the above relationships observed.An excellent conformity of results are observed for potentiometric, iodometric and volumetric (cerimetric) titration data for the estimation of ceriumin cerium salt solutions containing another oxidizing agent like Fe3+ions.