Analysis of rare earth sulfides, selenides and tellurides

The rare earth content of sulfides, selenides and tellurides is determined by titration with EDTA using Xylenol Orange as indicator. Sulfur is measured by titration of sulfate with lead nitrate solution after removal of rare earths on a cation exchanger. Selenium metal is precipitated from hydrochloric-sulfurous acid solution. Metallic tellurium is deposited from strongly acidic solutions containing sulfurous acid and hydrazine sulfate. An evaluation of the accuracy and precision of these methods is made.