Browsing by Author "Tewolde Bereket"

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    Hexafluorotantalate(V) – Selective Coated-Graphite Electrode
    (Addis Ababa Universty, 1993-06) Tewolde Bereket; Chandravanshi B.S. (PhD)
    The Hexafluorotantalate(V)-selective coated-graphite electrode was prepared by using a Brilliant Greenhexafluorotantalate( V) extract in 1-chloronaphthalene with a PVC matrix. The electrode body was prepared by fixing a graphite rod to one end of a glass tube housing a copper coil, so that the electrode is in contact with it. The potential measurement with the coated-graphite electrode was made against a sintered ground glass diaphragm (Ag/AgCl) external reference electrode. The concentrations of sulphuric and hydrofluoric acids, for optimum response of the electrode to hexafluorotantalate (V) were found to be 1 M in the test solutions. The response characteristics of the electrode have been evaluated, and the electrode was found to respond to hexafluorotantalate(V) in the concentration range of 5.0 x 10~ - 5.0 X 10-3 M tantalum (V) with a Nernstian slope ( 58±1 mV per decade) and the detection limit of 8.0 x 10-7 M. The effects of forty diverse ions on the electrode response to the hexafluorotantalate (V) have been studied to evaluate the selectivity of the electrode, and the electrode was found to be highly selective to hexafluorotantalate(V). The newly developed coated-graphite electrode has been applied to the determination of tantalum in tantalite-columbite ores and several artificial matrices by direct, standard addition, sample addition and Gran's plot potentiometric techniques. The experimental results are found to be in good agreement with the actual or certified values.