Extraction of SO₃H-containing iron (III) complexes with quaternary ammonium ions

Abstract

Extractability of iron (III) complexes with ο-dihydroxy derivatives containing-SO₃H group has been investigated in the presence of quaternary ammonium ions.
In the presence of dialkyl monomethyl benzylammonium chloride as quaternary ammonium salt, the complex having iron (III) -ligand mole ratio of 1 : 2 or 1 : 3 can be extracted into organic solvents, but the complex of 1 : 1 composition can not. Absorption spectrum of the complex in organic phase is similar to that in aqueous phase. Sulfonic anion is more beneficial than carboxylic anion among the functional groups used for the extraction of the complex, and these organic acid anions combine stoichiometrically with quaternary ammonium ion. The effect of ClO₄-is greater than Cl-.
The complex can be extracted into various organic solvents with dialkyl monomethyl benzylammonium ion, but can not with trimethyl benzylammonium ion. With tetradecyl dimethyl benzylammonium ion, the extractability of the complex depends on polarity of solvents and increases with increasing polarity.
This result is applicable to the separation of molybdenum (VI) from iron (III), titanium (IV) and vanadium (V), and the spectrophotometric determination of molybdenum (VI) in the presence of tungsten (VI).