SPECTROPHOTOMETRIC ESTIMATION OF RHENIUM WITH 5-CHLORO-2-HYDROXYTHIOBENZHYDRAZIDE AFTER ITS EXTRACTION SEPARATION USING N-OCTYLANILINE

A solution of n-octylaniline in chloroform extracts rhenium selectivel y from 0.12-0.16 M nitric acid medium. Rhenium from the organic phase is backstripped with 5% aqueous ammonia solution and estimated spectro photometrically with 5-chloro-2-hydroxythiobenzhydrazide (5-Cl-2-OHTBH ). 5-Cl-2-OHTBH forms a blue complex with rhenium on heating in the ac idity range 0.40-3.5 M HCl. The complex is extracted into chloroform a nd its absorbance is measured at 580 nm. The complex is stable for mor e than 12 h with a molar extinction coefficient of 9.0 x 10(3)l mole(- 1) cm(-1) and a Sandell sensitivity of 0.019 mu g cm(-2).