RESUMO
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.
RESUMO
Osmium was determined spectrophotometrically after coprecipitation with 5-chloro-2-hydroxythiobenzhydrazide at room temperature in the pH range 2.5-5.0 and collection on microcrystalline naphthalene. Beer's law was obeyed in the concentration range 1.8-14.4 ppm of osmium in a chloroform solution at 510 nm. The molar absorptivity and Sandell sensitivity were 1.056 x 10(4) l mol(-1) cm(-1) and 0.018 ppm, respectively. Six replicate analyses of a solution containing 7.2 ppm of osmium gave a mean absorbance of 0.405 with a standard deviation of 0.013 and a relative standard deviation of 0.92%. The complex was stable for over 72 h. The metal-to-ligand ratio in the complex was 1:2. Interference from various ions was studied, and the method was applied to the determination of osmium in various synthetic mixtures containing commonly associated metals and corresponding to the alloy composition. The sequential separation and determination of osmium and platinum is reported.