Spectrophotometric determination of palladium and iridium after extraction of their 1-phenyl-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiolates into molten naphthalene

A selective spectrophotometric method is described for the determination of palladium and iridium after extraction of their 1-phenyl-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiolates into molten naphthalene. The solid naphthalene containing the metal complex is separated by filtration and dissolved in chloroform. The absorbance is measured at 430 nm against a reagent blank in both instances. Beer's law is obeyed over the concentration range 3.0–25.5 p.p.m. for palladium and 3.8–42.0 p.p.m. for iridium. The molar absorptivities and Sandell's sensitivities are 4.066 × 103 l mol–1 cm–1 and 0.026 µg cm–2 for palladium and 3.879 × 103 l mol–1 cm–1 and 0.049 µg cm–2 for iridium. The mean absorbances for 15 p.p.m. of palladium and 23 p.p.m. of iridium are 0.573 and 0.464 with standard deviations of 0.0028 and 0.0054 and relative standard deviations of 0.94% and 0.60%, respectively. The interference of various ions has been studied in detail and the method has been applied to the simultaneous determination of palladium and iridium in certain synthetic samples.