Spectrophotometric determination of traces of platinum with 5-chloro-2-hydroxythiobenzhydrazide after extraction into molten naphthalene.

Platinum(IV) can be determined spectrophotometrically with 5-chloro-2-hydroxythiobenzhydrazide on extraction into molten naphthalene from the aqueous phase with pH 2.2-6.0. Beer's law is obeyed in the concentration range 1.0-7.0 microg cm(-2) of Pt(IV) in 4-methyl-2-pentanone solution at 680 nm. The molar absorptivity and Sandell sensitivity are found to be 2.40 x 10(4) L mol(-1) cm(-1) and 8.0 ng cm(-2), respectively. Six replicate analyses of a solution containing 40.0 microg of Pt(IV) gave a mean absorbance of 0.505 with a standard deviation of 0.0065 and a coefficient of variation of 1.30%. The complex is stable for more than 48 h. The metal to ligand ratio in the complex is determined to be 1:1. Interference from various ions is studied and the method is found to be selective for platinum. Platinum is determined in various synthetic mixtures and in some alloy samples. The method permits the sequential separation and determination of different amounts of platinum and rhenium from their mixtures.