Spectrophotometric determination of trace level thorium with n-phenylbenzohydroxamic acid

A method for the determination of thorium(IV) based on thorium-PBHA complex, which is extracted into amyl alcohol, is described. The thorium is back-extracted from amyl alcohol with 0.2M hydrochloric acid and estimated spectrophotometrically with thorin. The system has a maximum absorbance at 545 nm and obeys Beer's law between 0.5 to 12.5 ppm and the molar absorption coefficients is 1.7·10 1·mol^?1·cm^?1., Various parameters for the extraction and back-extraction and the effect of diverse ions have been studied.