P

Phenol red

IUPAC: 4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]phenol

C19H14O5S Indicators CAS 143-74-8
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Quick Reference
Formula / NotationC19H14O5S
CAS Number143-74-8
Molecular Weight354.4
AppearanceOdorless, red solid; Available as pure compound, soluble monosodium salt, and dilute solutions; [CHEMINFO]
Also Known As4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]phenol; phenolsulfonphthalein; 143-74-8; Fenolipuna; Sulphonthal; Phenolsulphonphthalein; PSP (indicator); NSC-10459; DTXSID8022408; I6G9Y0J1OJ
CategoryIndicators

What is Phenol red?

Phenol red is 3H-2,1-Benzoxathiole 1,1-dioxide in which both of the hydrogens at position 3 have been substituted by 4-hydroxyphenyl groups. A pH indicator changing colour from yellow below pH 6.8 to bright pink above pH 8.2, it is commonly used as an indicator in cell cultures and in home swimming pool test kits. It is also used in the (now infrequently performed) phenolsulfonphthalein (PSP) test for estimation of overall blood flow through the kidney. It has a role as a diagnostic agent, an acid-base indicator and a two-colour indicator. It is a member of phenols, a 2,1-benzoxathiole, a sultone and an arenesulfonate ester.

Formula & Notation

C19H14O5S

IUPAC Name: 4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]phenol

Other Names / Synonyms: 4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]phenol; phenolsulfonphthalein; 143-74-8; Fenolipuna; Sulphonthal; Phenolsulphonphthalein; PSP (indicator); NSC-10459; DTXSID8022408; I6G9Y0J1OJ

Properties & Characteristics

Appearance: Odorless, red solid; Available as pure compound, soluble monosodium salt, and dilute solutions; [CHEMINFO]. Molecular formula: C19H14O5S. Molecular weight: 354.4 g/mol. LogP: 3.

Physical Data

PropertyValue
Molecular Weight354.4
AppearanceOdorless, red solid; Available as pure compound, soluble monosodium salt, and dilute solutions; [CHEMINFO]

Uses & Applications

Used as a pH indicator in acid-base titrations, analytical chemistry, and chemical education demonstrations.

Safety Information

May be irritant or toxic in concentrated form. Handle with care. Consult SDS before use.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Phenol red
Formula C19H14O5S
CAS Number 143-74-8
Molecular Weight 354.4
Category Indicators
Synonyms 4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]phenol; phenolsulfonphthalein; 143-74-8; Fenolipuna; Sulphonthal; Phenolsulphonphthalein; PSP (indicator); NSC-10459; DTXSID8022408; I6G9Y0J1OJ

Frequently Asked Questions

Phenol red is 3H-2,1-Benzoxathiole 1,1-dioxide in which both of the hydrogens at position 3 have been substituted by 4-hydroxyphenyl groups. A pH indicator changing colour from yellow below pH 6.8 to bright pink above pH 8.2, it is commonly used as an indicator in cell cultures and in home swimming pool test kits. It is also used in the (now infrequently performed) phenolsulfonphthalein (PSP) test for estimation of overall blood flow through the kidney. It has a role as a diagnostic agent, an acid-base indicator and a two-colour indicator. It is a member of phenols, a 2,1-benzoxathiole, a sultone and an arenesulfonate ester.

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Editorial standards: Chemical data is sourced from peer-reviewed literature, CAS Registry, NIST WebBook, and PubChem. Safety information reflects guidance from OSHA, ECHA, and IAEA. For educational purposes only — always consult official SDS documentation and qualified professionals before handling chemicals.