Colorimetric determination of Fe2+/Fe3+
Colorimetric determination of Fe2+/Fe3+ after sample dissolution in concentrated HF; the Fe2+/Fe3+ ratio is preserved using the reversible reaction with V5+: Fe2+ + V5+ ⇔ Fe3+ + V4+, measurement of the absorption in visible light (Shimadzu UV 1800) caused by a red Fe2+-2,2-Bipyridil-complex; determination of total Fe in the same solution via complete reduction of Fe3+; small amounts of sample needed (2-50 mg); min. FeO concentration in the sample is 0.5wt% FeO.
Determination of Fe2+/Fe3+- ratio of solid materials such as minerals, glasses and rocks.
Schuessler, J.A., Botcharnikov, R.E., Behrens, H., Misiti, V., Freda, C. (2008): Oxidation state of iron in hydrous phono-tephritic melts, American Mineralogist 93 (10) , pp. 1493-1504