Electrochemical dating of archaeological gold based on refined peak current determinations and Tafel analysis

Abstract

This report proposes a refined method to date archaeological gold samples based on the Tafel analysis of the ascending part of voltammetric curves corresponding to the oxidation of surface flakes of gold in contact with hydrochloric acid aqueous electrolyte. This allows estimating the equilibrium potential of gold oxidation correcting for irreversibility effects. This equilibrium potential can be correlated with the coverage of adsorbed oxygen species and hence the estimated age of the gold samples. A satisfactory potential/time calibration graph was constructed from a set of archaeological samples including two sets of samples from the Mapungubwe Gold Collection, South Africa (1200–1290 CE) and Santa Llúcia, Alcalà de Xivert in Spain (dated back 600-550 BCE) sites. The dated samples come not only from different continents, but their ages also cover more than 3000 years.