Used as a reference material for calibrating instruments and validating analytical methods in environmental testing laboratories. Ensures accurate measurement of sulfide levels in water samples, supporting compliance with regulatory requirements for wastewater discharge and surface water quality monitoring. Helps maintain consistency and reliability in detecting sulfide concentrations, which is critical for assessing pollution levels, controlling odor in sewage systems, and protecting aquatic life. Commonly employed in municipal water treatment plants, industrial effluent monitoring, and environmental research studies.