Thymol blue

Thymol blue (thymolsulfonephthalein) is a brownish-green or reddish-brown crystalline powder that is used as a pH indicator.

It is insoluble in water but soluble in alcohol and dilute alkali solutions.

At wavelength (378 - 382) nm, extinction coefficient > 8000 and at wavelength (298 - 302) nm, the extinction coefficient > 12000.

[3] Thymol blue has different structures at different pH.

[4] Harmful if swallowed, Acute Toxicity.

NFPA 704 four-colored diamond Health 1: Exposure would cause irritation but only minor residual injury. E.g. turpentine Flammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oil Instability (yellow): no hazard code Special hazards (white): no code
Color of thymol blue solution at different acid-base conditions: left: acidic, middle: neutral, right: alkaline