POLAROGRAPHIC-DETERMINATION OF TOTAL IRON, IRON(II) AND IRON(III) IN ZINC PLANT ELECTROLYTE

Polarographic methods for the determination of iron(II), iron(III) and total iron in zinc plant electrolyte have been investigated. To provide a suitable medium for the determination, an aliquot of zinc plant electrolyte is added to a 0.1 M citrate-0.1 M EDTA solution and adjusted to pH 6.0 with ammonia. Polarograms recorded under these conditions provide a reversible Fe(III)+e - reversible Fe(II) response which is essentially independent of whether iron(II) or iron(III) standard solutions are used for calibration purposes. The media used eliminates interference from copper and precipitation of insoluble materials which occurs with more commonly used electrolytes for the polarographic determination of iron. Measurement of the differential pulse and current sampled dc polarograms followed by sequential addition of iron(II) and iron(III) iron standards provides an efficient method for the simultaneous determination of total iron, iron(II) and iron(III) in the 30-100 mg l-1 range. However, while the results for the total iron method can be validated, it has not been possible to establish whether or not transport of plant electrolyte circulating at elevated temperatures to a polarographic cell maintained at ambient temperature modifies the ratio of the two oxidation states.