This 400 NTU turbidity standard solution is used to calibrate and verify the accuracy of turbidimeters and nephelometers in water quality testing. It ensures consistent measurement of turbidity in drinking water, wastewater, and environmental samples. Commonly used in laboratories, water treatment plants, and pharmaceutical industries to meet regulatory standards such as those from EPA and USP. Provides a stable reference point for validating instrument performance and maintaining compliance in quality control procedures.