Solvent Extraction and Spectrophotometric Determination of Rhenium(Vll) using Mixed Ligands

Department of Chemistry, University of Calicut, Kerala·673 635

Manuscript received 6 July 1976, revised 4 October 1977, accepted 1 February 1978

A new method is proposed for the extraction and spectrophotometric determination of rheniom(Vll) using 2-mercaptobenzo-\(\gamma\)-thiopyrone (MBTP) and ammonium thiocyanate. as mixed ligands. The colour formation is complete in 30 min. and the complex is stable for over 24 hr at room temperature. The complex is formed in 1.8-1.6 N HCl medium and is extraeted into acetophenone, giving an absorbance maximum at 435 om. The method is more sensitive than any of the other spectrophotometric methods reported for rhenium. Many commonly associated ions do not interfere ; while serious interferences from Mo⁶⁺, W⁶⁺, U⁶⁺, V⁵⁺, Se⁴⁺, Ni²⁺, and Cu²⁺ are eliminated by a chloroform-tertiary amine extraction prior to the determination of rhenium. An improved method for the separation of molybdenum(Vl) before the determination of rhenium is also developed. Three substituted derivatives of MBTP have also been tried as mixed ligands with ammonium thiocyanate.