Used as a pH indicator in acid-base titrations, particularly for weak acid-strong base reactions. Changes color from red to yellow in the pH range 1.2–2.8 (first transition) and from yellow to blue in the pH range 8.0–9.6 (second transition). Commonly used in educational labs to demonstrate pH changes and in analytical chemistry for determining endpoint in titrations. Also applied in microbiology for some culture media to monitor pH shifts during bacterial growth.