An effective spectrophotometric determination of platinum with 1-(2-pyridylazo)-2-naphthol (PAN) using molten naphthalene as a diluent was studied. A green complex of platinum with PAN is formed at 90°C. In the range of pH 2.5-6.5,the complex is quantitatively extracted into molten naphthalene. The organic phase is anhydrously dissolved in CHC13 to be determined spectrophotometrically at 690 nm against the reagent blank. Beers law is obeyed over the concentration range tively. The optimum conditions for determination are obtained. The interferences of various ions are observed in detail. The method has been applied to the determination of platinum in synthetic samples.