Used in iodometric titrations to determine the concentration of oxidizing agents such as chlorine, bromine, and hydrogen peroxide. It reacts with iodine to form sodium tetrathionate and iodide, serving as a reliable reducing agent in redox titrations. Commonly applied in water quality testing to measure residual chlorine in drinking water and swimming pools. Also used in analytical laboratories for standardizing iodine solutions and in the determination of dissolved oxygen in water via the Winkler method. Its precise concentration makes it suitable for volumetric analysis where accuracy is critical.