Determination of iron(II) in rock, soil and clay

Abstract

A rapid and direct method for the determination of iron(II) in silicates is described. Redox processes frequently occurring during decomposition are suppressed satisfactorily by limiting the reaction time to 10 s while maintaining the temperature at 60–65 °C. Reproducible decomposition temperatures are achieved by mixing concentrated sulphuric and hydrofluoric acids (1 + 3 V/V) in the reaction vessel. The coloured iron(II)-1, 10-phenanthroline complex is used in the spectrophotometric determination of the two valency states of iron, iron(II) directly and iron(III) by difference after subsequent reduction by hydroquinone. Mean results of duplicates of the USGS geological standards G-2, AGV-1 and BCR-1 are within 0.1% and those for DTS-1 and PCC-1 within 0.3% of the quoted average values for iron(II) oxide.