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 provi de a suitable medium for the determination, an aliquot of zinc plant e lectrolyte is added to a 0.1 M citrate-0.1 M EDTA solution and adjuste d to pH 6.0 with ammonia. Polarograms recorded under these conditions provide a reversible Fe(III)+e - reversible Fe(II) response which is e ssentially independent of whether iron(II) or iron(III) standard solut ions are used for calibration purposes. The media used eliminates inte rference from copper and precipitation of insoluble materials which oc curs with more commonly used electrolytes for the polarographic determ ination of iron. Measurement of the differential pulse and current sam pled dc polarograms followed by sequential addition of iron(II) and ir on(III) iron standards provides an efficient method for the simultaneo us determination of total iron, iron(II) and iron(III) in the 30-100 m g 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 tra nsport of plant electrolyte circulating at elevated temperatures to a polarographic cell maintained at ambient temperature modifies the rati o of the two oxidation states.