Coulometric Titration of Niobium in 1F Sulfuric Acid

Department of Chemistry, Federal City College Washington, D.C. 20005 U.S.A. Manuscript received 30 September 1974; accepted 17 March 1975 A coulometric titration at constant current has been devsied for Nb in 1F sulfuric acid. The titration was based on the oxidation of Nb(III) to Nb(V) by Fe(III) electrogenerated at a graphite anode. Both potentiometric and amperometric end points were used. The Nb(V) was prior reduced at a mercury cathode by exhaustive electrolysis at a current density of 15 ma/cm2 for at least 10 hr. Ta, V, Ti and a working platinum anode interfered, but the seperation of the potentials of Nb(V)/Nb (III) and Ti(IV)/Ti(III) permitted the titration of first Nb and then Ti. The average error for the titration of 0.30 to 13.00 mg of niobium in 100 ml of LIP sulfuric acid was + 0.57%