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Thymol blue
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<p>Thymol blue (thymolsulfonephthalein) is a brownish-green or reddish-brown crystalline powder that is used as a <a href="/facts/PH_indicator/Levp3yqq">pH indicator</a>. It is insoluble in <a href="/facts/Water/0lkXnJPK">water</a> but soluble in <a href="/facts/Ethanol/3lCLfBSP">alcohol</a> and dilute <a href="/facts/Alkali/s6NqPGSP">alkali</a> solutions. </p> <p>It transitions from red to yellow at <a href="/facts/PH/RnSv8D7y">pH</a> 1.2–2.8 and from yellow to blue at pH 8.0–9.6. It is usually a component of <a href="/facts/Universal_indicator/7EtUFw6w">Universal indicator</a>. </p><p>At wavelength (378 - 382) nm, extinction coefficient > 8000 and at wavelength (298 - 302) nm, the extinction coefficient > 12000. </p>