Spectrophotometric Determination of Palladium in Titanium Alloys

Abstract

A spectrophotometric method for the determination of palladium in titanium alloys has been developed by the use of palladium-tin chloride system. The reaction of palladium (II) with tin (II) in hydrochloric acid has a very interesting process in its color development. Absorption spectra were obtained only in two forms of which one is that of initial yellow complex and the other that of final green. Even the well-known green complexes of palladium still showed the changes of color quality in the visible region, particularly near ultra-violet, with lapse of time. But it was found that the absorbance of the green complexes shows only a negligible change at 635 mμ region and the spectrophotometric method is useful for the determiation. Dissolve 0.5 g of sample in 5 mL of 2 M citric, 16 mL of 6 N hydrochloric, and 6 mL of 11.5 N hydrofluoric acids. When the reaction subsides,add 3 mL of 16N nitric acid, and heat the solution gently until dissolution is complete. Add 1.5 g of boric acid and 2 g of urea, and dissolve completely. Cool the solution to 20°C, and add 5 mL of 0.5 M stannous chloride. Transfer the solution to a 50 mL calibrated flask, dilute to the mark with water, and mix well. Let stand for 15min, and obtain the absorbance of the solution at 635 mμ within 30 min. Under the conditions, the system conforms practically to Beer’s law, as given by 2.4×10³ for the molecular extinction coefficient of palladium. Many elements normally found in titanium alloys cause no interference except molybdenum. The coefficient of deviation is less than 2.6 percent at 0.05∼5 percent palladium level.