Spectrophotometric determination of trace amounts of iron in pure reagent chemicals by solvent extraction as the ternary complex of iron(II), 4-chloro-2-nitrosophenol and Rhodamine B

Abstract

Trace amounts of iron in pure reagent chemicals have been determined by solvent extraction-spectrophotometry with 4-chloro-2-nitrosophenol and Rhodamine B. The ternary complex of iron(II), 4-chloro-2-nitrosophenol and Rhodamine B was extracted quantitatively into toluene at about pH 4.8. The absorbance of the organic phase was measured in a glass cell of 10-mm path length at 558 nm. The apparent molar absorptivity of the ternary complex in the organic phase was 9.0 × 10⁴ l mol^–1 cm^–1 at 558 nm. The ternary complex was very stable and not decomposed by addition of EDTA. By using the above procedure, trace amounts of iron (10^–7–10^–4%) in alkali metal salts, alkaline earth metal salts, ammonium salts, acids and bases, etc., were determined. The standard deviations of the determinations were 1–3%.