Bromothymol blue is a pH indicator commonly used in laboratories to measure acidity and alkalinity. It changes color depending on the pH level of a solution: it appears yellow in acidic conditions (pH below 6), green at neutral pH (around 7), and blue in basic conditions (pH above 7.6). This compound is often utilized in various applications, including biology experiments and water quality testing. Its ability to visually indicate pH changes makes it a valuable tool for educators and researchers alike, helping to demonstrate chemical reactions and the properties of acids and bases.