Formation of Soluble Iron (III) Complexes with Triethanolamine and Related Compounds as Studied by Magnetic Susceptibility Measurements

Abstract

Magnetic susceptibility measurements for the aqueous iron (III) -triethanolamine (TEA) systems of [iron (III) ion] =2.5 mM ( 1 M=1 mol dm^-3) and R= [TEA]/ [iron (III) ion] ≥ 20 in a wide pH range 1 to 13 at room temperature have been carried out by the Gouy method with much attention to precipitation reactions in these solutions. It has been revealed that, at pH 3-7, TEA scarcely solubilizes iron (III) hydroxide-like clusters, while, at pH> 8, it strongly coordinates to an iron (III) ion with its deprotonated hydroxyethyl group and finally forms some stable and soluble mononuclear iron (III) complex with a TEA/Fe ratio of 2 or 3. It appears well established that the masking of iron (III) ions by TEA in analytical chemistry is identical with the formation of the above-mentioned mononuclear iron (III) complex in alkaline media.