Base indicator, pH 1.2 (red) ~ 2.8 (yellow), 8.0 (yellow) ~ 9.6 (blue).
An anionic surfactant indicator that turns reddish purple when anionic surfactants are encountered under acidic conditions.
A mixture of thymol blue, cresol red, ethanol, sodium bicarbonate, and potassium chloride can be used to form a bicarbonate indicator to identify the presence of carbon dioxide.