Thymolphthalein is a synthetic phthalein dye and acid-base indicator with the chemical formula C₂₈H₃₀O₄. It is colorless under acidic to near-neutral conditions and develops a blue color in alkaline solutions. Its sharp color transition occurs at approximately pH 9.3–10.5, making it suitable for detecting strongly basic conditions. The blue form of Thymolphthalein shows strong light absorption at around 595 nm. It is primarily used as a pH indicator in analytical chemistry.
CAS No.: 125-20-2
Synonyms: Thymol peptide, Thymolphthalein indicator.
| Physical Properties | |
| Chemical formula | C28H30O4 |
| IUPAC Name | 3,3-Bis[4-hydroxy-2-methyl-5-(propan-2-yl) phenyl]-2-benzofuran-1(3H)-one |
| Molecular weight | 430.544Â g/mol |
| Solubility | Soluble in water |
| Ph | 9.3-10.5, colorless to blue |
| Density | 0.79 g/cm3 |
| Flash Point | 21°C |
| Storage | Store at room temperature |
| Chemical Properties | |
| Color | Clear-colorless |
| Physical State | Liquid |
| Melting Point | 251-253 °C |
| λmax | 592-596 nm |
| Odor | Odorless |
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| Pictograms : |   |
| Hazard Statements : | H225: Highly flammable liquid and vapour. H319: Causes serious eye irritation. |
| Precautionary Statements: | P210: Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking. P305+P351+P338: IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. P403+P233: Store in a well-ventilated place. Keep container tightly closed. |
Thymolphthalein is a synthetic phthalein dye and acid-base indicator with the chemical formula C₂₈H₃₀O₄. It is colorless under acidic to near-neutral conditions and develops a blue color in alkaline solutions. Its sharp color transition occurs at approximately pH 9.3–10.5, making it suitable for detecting strongly basic conditions. The blue form of Thymolphthalein shows strong light absorption at around 595 nm. It is primarily used as a pH indicator in analytical chemistry.
CAS No.: 125-20-2
Synonyms: Thymol peptide, Thymolphthalein indicator.
| Physical Properties | |
| Chemical formula | C28H30O4 |
| IUPAC Name | 3,3-Bis[4-hydroxy-2-methyl-5-(propan-2-yl) phenyl]-2-benzofuran-1(3H)-one |
| Molecular weight | 430.544Â g/mol |
| Solubility | Soluble in water |
| Ph | 9.3-10.5, colorless to blue |
| Density | 0.79 g/cm3 |
| Flash Point | 21°C |
| Storage | Store at room temperature |
| Chemical Properties | |
| Color | Clear-colorless |
| Physical State | Liquid |
| Melting Point | 251-253 °C |
| λmax | 592-596 nm |
| Odor | Odorless |
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| Pictograms : | |
| Hazard Statements : | H225: Highly flammable liquid and vapour. H319: Causes serious eye irritation. |
| Precautionary Statements: | P210: Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking. P305+P351+P338: IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing. P403+P233: Store in a well-ventilated place. Keep container tightly closed. |
Thymolphthalein is an organic phthalein dye used mainly as an acid–base (pH) indicator in analytical chemistry, particularly for detecting alkaline conditions. It is also used in disappearing ink, educational demonstrations, and research applications.
A Thymolphthalein indicator solution can be prepared by dissolving the dye in 95% ethanol and diluting it with distilled water to the required volume.
Thymolphthalein and Phenolphthalein both are synthetic acid–base pH indicators but they differ in their pH transition ranges and color changes. Thymolphthalein changes from colorless to blue at approximately pH 9.3–10.5, while Phenolphthalein changes from colorless to pink in a lower alkaline pH range.
