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.
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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
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Identifiers | |
3D model (JSmol)
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ChemSpider | |
ECHA InfoCard | 100.000.886 |
EC Number |
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PubChem CID
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
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] |
Insoluble | |
UV-vis (λmax) | 594 nm (1st) 376 nm (2nd)[1] |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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Harmful |
GHS labelling:[2] | |
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Warning | |
H302 | |
P264, P270, P301+P312, P330, P501 | |
NFPA 704 (fire diamond) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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
editThymol blue has different structures at different pH.
Safety
editIt may cause irritation. Its toxicological properties have not been fully investigated.[4] Harmful if swallowed, Acute Toxicity. Only Hazardous when percent values are above 10%.[5]
Bibliography
edit- Merck. "Thymol Blue." The Merck Index. 14th ed. 2006. Accessed via web on 2007-02-25.
References
edit- ^ a b Thymol Blue
- ^ "Thymol blue". pubchem.ncbi.nlm.nih.gov. Retrieved 12 December 2021.
- ^ "Product Specification: Thymol Blue- ACS reagent" (PDF). Sigma-Aldrich. 9 October 2017. p. 1.
- ^ "Thymol Blue MSDS". Fisher Scientific. Retrieved 2024-07-23.
- ^ "Thymol blue". PubChem. Retrieved 2017-10-09.
External links
editWikimedia Commons has media related to Thymol blue.