Determination of iron(II) in silicates by gravimetric titration

Abstract

A rapid method, suitable for batch working, is described for determining iron(II) in silicates. Hot 1 + 1 hydrofluoric-sulphuric acid decomposes the subsample in a polypropylene bottle previously filled with carbon dioxide. After dilution with a boric-phosphoric-sulphuric acid mixture, iron(II) is titrated gravimetrically with potassium dichromate solution, in the bottle used for sample decomposition. A sample-preparation procedure that minimises oxidation of iron(II) is described. Results obtained for iron(II) in various international reference rocks by the proposed method agree well with recommended values.