Thymol blue
Names | |
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Preferred IUPAC name 3,3-Bis[4-hydroxy-2-methyl-5-(propan-2-yl)phenyl]-2,1λ6-benzoxathiole-1,1(3H)-dione | |
Other names α-hydroxy-α,α-bis(5-hydroxycarvacryl)- o-toluenesulfonic acid γ-sultone; thymolsulfonephthalein | |
Identifiers | |
CAS Number |
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3D model (JSmol) |
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ChemSpider |
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ECHA InfoCard | 100.000.886 |
EC Number |
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PubChem CID |
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UNII |
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CompTox Dashboard (EPA) |
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InChI
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Properties | |
Chemical formula | C27H30O5S |
Molar mass | 466.59 g·mol−1 |
Appearance | Brownish-green crystal powder |
Melting point | 221–224 °C (430–435 °F; 494–497 K) decomposes[1] |
Solubility in water | Insoluble |
UV-vis (λmax) | 594 nm (1st) 376 nm (2nd)[1] |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards | Harmful |
GHS labelling:[2] | |
Pictograms | |
Warning | |
Hazard statements | H302 |
Precautionary statements | P264, P270, P301+P312, P330, P501 |
NFPA 704 (fire diamond) | 1 1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references |
Chemical compound
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.
Thymol blue (pH indicator) | ||
below pH 8.0 | above pH 9.6 | |
8.0 | ⇌ | 9.6 |
Thymol blue (pH indicator) | ||
below pH 1.2 | above pH 2.8 | |
1.2 | ⇌ | 2.8 |
It transitions from red to yellow at pH 1.2–2.8 and from yellow to blue at pH 8.0–9.6. It is usually a component of Universal indicator.
At wavelength (378 - 382) nm, extinction coefficient > 8000 and at wavelength (298 - 302) nm , the extinction coefficient > 12000.[3]
Structures
Thymol blue has different structures at different pH.
- thymol blue.
Safety
It may cause irritation. Its toxicological properties have not been fully investigated. Harmful if swallowed, Acute Toxicity. Only Hazardous when percent values are above 10%.[4]
Bibliography
- Merck. "Thymol Blue." The Merck Index. 14th ed. 2006. Accessed via web on 2007-02-25.
References
External links
Wikimedia Commons has media related to Thymol blue.
- PubChem entry