This is one of the best methods for the determination of the element. Gold must be absent, for it precipitates as the metal even from cold solutions. The platinum metals do not, in general, interfere but moderate amounts of platinum may cause a little contamination of the precipitate, and with large amounts a second precipitation is desirable. The precipitate is decomposed by digestion on the water bath with a little aqua regia, and diluted with an equal volume of water; the resulting solution is largely diluted with water, and the palladium re-precipitated with dimethylglyoxime.
An objection to the precipitation of palladium with dimethylglyoxime is the voluminous character of the precipitate. Hence if much palladium is present, an aliquot part of the solution should be used.
The solution should contain not more than 0.1 g Pd in 250 mL, be 0.25M with respect to hydrochloric or nitric acid, and be free from nickel and gold. Add, at room temperature, a 1 per cent solution of dimethylglyoxime in 95 per cent ethanol. Use 2-5 mL of the reagent for every 10 mg of palladium. Allow the solution to stand for 1 hour, and then filter through a weighed filtering crucible (sintered-glass, or porcelain). Test the filtrate with a little of the reagent to make sure that precipitation is complete. Wash the orange-yellow precipitate of palladium dimethylglyoximate thoroughly, first with cold water and then with hot water. Dry at 110 °C to constant weight. Weigh as Pd(C4H7O2N2)2.