Used in analytical chemistry for calibration and standardization of redox reactions, particularly in titrations involving iodine or chlorine. Commonly applied in water treatment labs to determine residual oxidants like free chlorine in drinking water and wastewater, and in treatment processes to dechlorinate by reducing excess chlorine to safe levels before discharge. Also utilized in the pulp and paper industry to measure and control bleaching processes, and as a reducing agent in pulping. Its standardized concentration ensures accurate dosing, reproducible results in quality control, and reliable environmental monitoring.