Amperometric Determination of V(V), Cr(III), Mn(VII), Cr(VI) and Fe(III) with 3-Mercaptopropanoic Acid

Abstract

Amperometric determination of V(V), Cr(III), Mn (VII), Cr (VI) and Fe (III) is reported with the help of 3-mercaptopropanoic acid (MPSH). The fundamental reaction involved in case of the first two species is complexation while that in case of Mn (VII) is oxidation of MPSH; the last two species do not interact chemically with the acid and the new methods reported are based on the phenomenon of current compensation. Metal ion: MPSH ratio is 1 : 2 for V(V) and Cr (III), 1 : 4 for Cr (VI) and 1 : 0.66 for Fe (III); this ratio for Mn (VII) is 1 : 1 if the metal ion is used as titrant and 2 : 1 if MPSH is used in that capacity. Tolerance for diverse foreign ions has also been worked out.