The Bromothymol blue-neutral red indicator solution is a pH indicator used in the range of 6.0 to 7.6, near neutral, for detecting subtle acidity-alkalinity changes.

Below pH 6.0, it turns red (from neutral red), above pH 7.6 it turns blue (from bromothymol blue), and green in between, indicating neutrality. This clear color transition makes it ideal for visual pH monitoring.

It is employed in microbiological and biochemical applications, particularly in culture media to detect acidity changes, and in bacterial growth studies where pH shifts signal metabolic activity.

Additionally, it is used in environmental testing for water quality monitoring, such as assessing carbon dioxide levels in aquatic systems via color change, and in diagnostic procedures like urine testing or educational lab experiments for pH determination.