Formazine standard solution is primarily used as a turbidity standard in water quality testing. It helps calibrate and verify the accuracy of turbidimeters, which measure the cloudiness or haziness of water caused by suspended particles. This solution is essential in environmental monitoring, ensuring compliance with regulatory standards for drinking water, wastewater, and industrial effluents. Its consistent turbidity levels make it a reliable reference for maintaining the precision of analytical instruments. Additionally, it is employed in research and development to simulate turbid conditions in laboratory studies.