Used as a pH indicator in analytical chemistry, bromothymol blue is especially effective for detecting weak acids and weak bases. It is commonly employed in laboratory settings to determine the presence of carbon dioxide in liquid solutions—such as in biological experiments where respiration or photosynthesis is monitored—due to the formation of carbonic acid, which changes the pH. The indicator turns yellow in acidic conditions, green at neutral pH, and blue in alkaline environments, making it ideal for educational demonstrations and titration experiments. It is also utilized in microbiological media to assess metabolic activity and in environmental testing to evaluate water quality.