Bromothymol Blue

Bromothymol Blue (BTB) is a sulfonephthalein-based pH indicator dye with a sharp and reversible color transition near neutrality: yellow in acidic conditions, blue in alkaline media, with a clear transition interval around pH 6.0-7.6. Bromothymol Blue is widely applied in analytical chemistry and education as a reliable acid-base indicator for titrations and demonstrations of pH changes. In microbiology and biotechnology it is incorporated into culture media to reveal microbial metabolism, acid formation, or carbon dioxide release, while in environmental monitoring it serves as a practical tool for assessing water quality and maintaining stable pH in aquaculture systems. The compound also finds use in physiological and medical research where it assists in the study of respiration, photosynthesis, and other pH-sensitive biochemical processes. Beyond the laboratory, Bromothymol Blue is a common component of indicator solutions and pH testing kits.