Used as a pH indicator in acid-base titrations, particularly for weak acid-strong base reactions. Changes color from red to yellow in acidic range (pH 1.2–2.8) and from yellow to blue in basic range (pH 8.0–9.6). Commonly used in educational labs to demonstrate pH transitions and in analytical chemistry for endpoint detection. Also applied in environmental testing to monitor water and soil pH where precise color change is needed. Suitable for use in both aqueous and mixed solvent systems due to good solubility and clear visual transition.