Aquomolybdenum(III) chloride as a reducing titrant A potentiometric study

• Published in: Talanta (Oxford) Vol. 23; no. 6; p. 427
• Main Authors: Sagi, S R, Rao, P R
• Format: Journal Article
• Language: English
• Published: Netherlands 01.06.1976
• ISSN: 0039-9140
• DOI: 10.1016/0039-9140(76)80122-1

The use of aquomolybdenum(III) chloride as a reducing agent for the direct potentiometric titration of Ce(IV), Cr(VI), Fe(III), V(V), Mo(VI), U(VI) and H(2)O(2) is described. The variation of the formal redox potentials of Mo(V)/Mo(IV) and Mo(IV)/Mo(III) in varying concentrations of hydrochloric, phosphoric and acetic acids is investigated. Aquomolybdenum(III) chloride is found to be a better reducing titrant than chloromolybdate(III) and gives better breaks in the titration curves. In the titration of molybdenum(VI) in 3M HCl the titration curve shows three jumps, corresponding to the reductions of Mo(VI) to Mo(V). and Mo(V) to Mo(IV) via an apparently intermediate oxidation state which presumably corresponds to a dimeric mixed-valence species. The aquomolybdenum(III) complex ion is a better reducing titrant than chloromolybdate(III) and has a wider applicability.