Investigation on oxidation states of rhenium in Re-HEDP

The oxidation states of rhenium in Re-HEDP (hydroxyethylidene diphosphonate) were measured bythe methods of extraction and potentiometric titration. The oxidation state of rhenium in Re-HEDP was mostly +4valence, and the Re(Ⅳ)-HEDP was oxidized to Re( Ⅴ)-HEDP when it was titrated by I3- at pH 2.0. In the reductionsystem of Vc+Sn2+ , ReO4- was only reduced by Sn2+, but Vc was oxidized earlier than Sn2+ when it was titrated by I3.