Used in analytical chemistry for redox titrations, particularly in the determination of oxidizing agents such as potassium permanganate, potassium dichromate, and hydrogen peroxide. It serves as a stable reducing agent with a known concentration, allowing for precise and accurate standardization of oxidant solutions. Commonly applied in water and wastewater analysis to measure chemical oxygen demand (COD), where it reacts with excess oxidant after digestion of the sample. Its role as a titrant ensures reliable quantification of oxygen demand and other redox-active species in environmental and industrial testing.