Iodometric titration for determining the oxygen content of samples doped with Fe and Co

Double iodometric titration is a method developed for high-T_c superconductivity. It has been widely used to determine the effective oxidation of copper and to figure out the oxygen content in a sample in the past years. If a sample is doped with some metals like iron and cobalt, these metal ions can interfere in experiment results. This is a major defect for iodometric titration. To solve this problem, we introduce ammonium hydrogen fluoride as a complex agent into the method. The agent can prevent the interference of ions of iron and cobalt. For samples LaBa₂Cu_3−xFe_xO_y and YBa₂Cu_3−xCo_xO_y, we determine the oxygen content by an improved double iodometric titration in which the ammonium hydrogen fluoride is used as an interference-free agent. For samples doped with a small amount of Fe or Co, experiment results agree well with those of other researchers. As to samples doped with a large amount of Fe or Co, we determine their values of oxygen content and the results are reasonable.