Development and Validation of a Low Cost Electrolytic Cell for Quantifying Copper in Jewelry: an Experimental Proposal for Teaching Analytical Instrumental Chemistry

Abstract

The quantitative determination of Cu in solution by electrodeposition on Pt electrode using instrumentation is a classic experiment in Instrumental Analytical Chemistry, to introduce the fundamentals of electrogravimetry. However, this practice cannot always be performed, given the high cost of Pt electrodes, which are generally not available in academic institutions. In this work, an alternative system was developed and validated. The Pt electrodes were replaced by a graphite rod extracted from an exhausted battery (anode) and copper, obtained from scraps of copper pipes from a refrigeration system (cathode). The deposition yields of the conventional (using Pt electrodes) and alternative systems were 100.6 ± 1.0% and 96.31 ± 2.64%, respectively. The alternative system was applied to determine the percentage of Cu (m/m) in a jewelry sample, obtaining 90.56 ± 1.37%. This work brings contributions to the works in the literature, where the efficiency of the alternative system is compared with that of the conventional system, and the pair of electrodes used as cathode and anode has not yet been used for Cu electrodeposition. The experiment was planned where the electrolysis time is approximately 1.5 h, and contributes to the economy of electric energy consumption and with the environment.