Determination of Cyanide Species in Silver and Gold Plating Solutions by Raman Spectroscopy

Raman spectra of silver and gold cyanide complexes have been investigated in order to determine the speciation of aqueous plating solutions. We have examined the ionic species in the concentration ranges of 0.003 ∼ 0.5 M for the metals and 0.1 ∼ 2.5 M for the cyanide ion. When the initial concentration of [Ag(CN)2]− was below ∼0.1 M, [Ag(CN)4]3– did not appear prominent even at high CN−/Ag(I) ratios of 3 ∼ 10, differing from the case of previous infrared measurements. Concentrations of the metal cyanide complexes and CN− ion as low as 0.001 ∼ 0.01 M could be determined with an error of less than ∼3% from the analysis of Raman peak areas.