Nitrazine yellow is primarily used as a pH indicator in various medical and laboratory applications. In clinical settings, it is employed to test the pH of bodily fluids, such as vaginal secretions, to determine conditions like amniotic fluid leakage during pregnancy. It helps distinguish between amniotic fluid and other discharges due to its sensitivity to pH changes. In laboratories, it is utilized in titrations and experiments where precise pH monitoring is required. Additionally, it finds use in industrial processes where pH control is critical, such as in water treatment and chemical manufacturing. Its ability to provide clear visual color changes makes it a valuable tool for quick and accurate pH assessment.