Development of Wet Chemical Analysis Technique for Tramp Elements (M = As, Pb, Sb, and Sn) in Silver-M Alloys

Wet chemical analysis techniques for four elements (M = As, Pb, Sb, and Sn) in Ag – M binaryalloys were investigated with emphasis on the choice of solvent acid and the characteristic wavelength usedin the ICP-AES (Inductively-Coupled Plasma Atomic Emission Spectrometer) analysis. The elements arerepresentative tramp elements in ferrous scrap. The activity of these elements needs to be increased to removethem efficiently during the molten scrap refining process. The activity of these elements in the molten scrap(molten iron alloy) is usually measured by a chemical equilibration technique with molten Ag. Therefore,performing an accurate and reliable chemical analysis of these elements in the molten iron alloy and themolten Ag alloy is important. Preliminary tests using conventional acids (hydrochloric acid, nitric acid)resulted in unreliable results. In the present study, the proper choice of acids as solvents was investigatedfor each element M in the Ag-M alloys. Several synthesized Ag-M alloys of known compositions were analyzedusing two ICP-AES systems independently, for cross-checking. As and Pb in Ag alloys could be successfullydissolved in the nitric acid-based solution. On the other hand, Sb and Sn in Ag alloys did not dissolve in thenitric acid-based solution completely, leaving some precipitates. It was found that the addition of hydrofluoricacid could resolve this problem. In addition to this, the effect of the mass of the Ag-M alloy and wavelengthselection during ICP-AES analysis on the accuracy and the reproducibility were investigated. An optimizedprocedure for the wet chemical analysis of these elements in Ag-M alloys is reported.