Determination of Ferrous Iron in the Presence of Ferric Iron With Bathophenanthroline

Many of the analytic procedures used for the determination of ferrous iron in the presence of ferric iron are not applicable to the determination of ferrous iron in natural waters because of a lack of sensitivity or because of the instability of developed color. The 1, 10‐phenanthroline method for the determination of ferrous iron, recommended in the ninth and tenth editions of Standard Methods, is likely to result in incorrect results unless it is applied in a very limited range and under special conditions. A colorimetric procedure using bathophenanthroline as the color‐developing reagent has been found to give reliable determinations of ferrous iron in the presence of ferric iron in quantities measured in micrograms.