Platinum, palladium, rhodium, ruthenium, iridium, and gold are determined by direct spectrographic analysis of a fire-assay silver bead. Fire-assay methods and standards preparation are described. The fire-assay bead is placed into a graphite electrode containing 3 mg of (NH4)2OsCL6 and arced at 15 A dc in an argon-oxygen atmosphere. With the methods outlined, detection limits for a 15-g sample are 1 ppb for Au and Pd, 2 ppb for Pt and Rh, and 100 ppb for Ru and Ir.
