Stoichiometry of superconducting YBa2Cu3Oy A comparison of methods for the determination of the Cu(I):Cu(II) ratio

Two methods for the determination of Cutot, Cu2+ and Cu+ in the superconductor YBa2Cu3Oy are described. The first one is based on two iodometric titrations. The second one is based on an indirect determination of Cu+ after oxidation with Fe3+ and titration with KMnO4 of the formed Fe2+. Sources of errors such as incomplete dissolution of the samples and oxidation by atmospheric oxygen are discussed. Precision and accuracy of the procedures are quoted and the performance of the two methods is compared.