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Indicators and stains

Phenol red

Also known as phenolsulfonphthalein, Fenolipuna, Sulphonthal

CAS 143-74-8Formula C19H14O5SMolar mass 354.38 g/molEC 205-609-7
GHS signal word: Warning. Pictograms: Harmful or irritant 97 suppliers listed
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Phenol red chemical structure, C19H14O5S, CAS 143-74-8
2D chemical structure

Key facts

What buyers check first

All properties
CAS number
143-74-8
Formula
C19H14O5S
Molar mass
354.38 g/mol
EC number
205-609-7
HS code
293499
Category
Indicators and stains

What is Phenol red?

Plain description, key identifiers and synonyms

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.

Identifiers

Registry numbers, names and line notations, tap to copy

IUPAC name
4-[3-(4-hydroxyphenyl)-1,1-dioxo-2,1ฮป6-benzoxathiol-3-yl]phenol
CAS number
143-74-8 CAS number cross-checked
EC number
205-609-7
Molecular formula
C19H14O5S
UNII
I6G9Y0J1OJ
MDL number
MFCD00003552
INCI name
PHENOLSULFONPHTHALEIN
InChIKey
BELBBZDIHDAJOR-UHFFFAOYSA-N
InChI
InChI=1S/C19H14O5S/c20-15-9-5-13(6-10-15)19(14-7-11-16(21)12-8-14)17-3-1-2-4-18(17)25(22,23)24-19/h1-12,20-21H
SMILES (canonical and isomeric)
C1=CC=C2C(=C1)C(OS2(=O)=O)(C3=CC=C(C=C3)O)C4=CC=C(C=C4)O

Synonyms

  • phenolsulfonphthalein
  • Fenolipuna
  • Sulphonthal
  • PSP (indicator)
  • Phenolsulphonphthalein
  • Phenol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis-, (S,S-dioxide)
  • 3,3-bis(4-hydroxyphenyl)-3H-2,1??-benzoxathiole-1,1-dione
  • 2-(Bis(4-hydroxyphenyl)methyliumyl)benzenesulfonate
  • Sulfonphthal
  • Sulphental
  • Phenolred
  • 3,3-Bis(4-hydroxyphenyl)-3H-benzo[c][1,2]oxathiole 1,1-dioxide
  • Phenolsulfonephthalein
  • Phenol, 4,4'-(1,1-dioxido-3H-2,1-benzoxathiol-3-ylidene)bis-
  • Phenol red solution
  • Phenol red indicator
  • 4-[3-(4-Hydroxyphenyl)-1,1-dioxo-2,1lambda6-benzoxathiol-3-yl]phenol
  • 4,4'-(3H-2,1-Benzoxathiol-3-ylidene)diphenol S,S-dioxide
  • 4,4'-(1,1-dioxido-3H-2,1-benzoxathiole-3,3-diyl)diphenol
  • 3H-2,1-Benzoxathiole, 3,3-bis(4-hydroxyphenyl)-, 1,1-dioxide
  • Phenol, 4,4-(3H-2,1-benzoxathiol-3-ylidene)di-, S-S-dioxide
  • P. S. P.
  • Phenol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)di-, S,S-dioxide
  • Phenol red, acs
  • 3,3-bis(4-hydroxyphenyl)benzo[c]1,2-oxathiolene-1,1-dione
Show all 36 synonyms
  • Phenol-red
  • Phenosulfophthalein
  • Phenolsulfonphthalein, 3,3-bis(4-hydroxyphenyl)-3H-2,1-benzoxathiole 1,1-dioxide, PSP
  • Phenol red, PSP
  • phenolsulphonephthalein
  • Phenol red ACS grade
  • Phenol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis-, S,S-dioxide
  • Phenol Red, ACS reagent
  • Phenol Red (>90%)
  • Phenol red, recrystallized
  • 5-19-03-00457 (Beilstein Handbook Reference)

Physical and chemical properties

Measured values and descriptors computed from the structure

Physical and chemical properties

Measured values, check the supplier specification for your grade

No measured properties are recorded for this substance yet. Ask suppliers for a technical data sheet.

Values vary by grade. Ask suppliers for the COA or TDS of the batch you buy.

Computed descriptors

Calculated from the structure, useful for screening and formulation

Molecular weight
354.38 g/molcalc.
Exact mass
354.0562 Dacalc.
LogP (octanol/water)
3.11calc.
Topological polar surface area
83.83 ร…ยฒcalc.
Hydrogen bond donors
2calc.
Hydrogen bond acceptors
5calc.
Rotatable bonds
2calc.
Heavy atoms
25calc.
Rings
4calc.
Aromatic rings
3calc.
Fraction sp3 carbons
0.05calc.
Formal charge
0calc.
Stereocentres
0calc.
Lipinski rule of five
Passes (0 violations)calc.

Calculated for screening. Confirm critical figures with the supplier.

Murcko scaffold

The ring system that remains when every side chain is removed

Murcko scaffold of this chemical, O=S1(=O)OC(c2ccccc2)(c2ccccc2)c2ccccc21

O=S1(=O)OC(c2ccccc2)(c2ccccc2)c2ccccc21

4 rings, 23 atoms, the 3,3-Diphenyl-3H-benzo[c][1,2]oxathiole 1,1-dioxide ring system.

63 other chemicals share this scaffold

Safety and hazards

GHS classification summary, not a safety data sheet

GHS signal word
Warning
GHS07: Harmful or irritant
Harmful or irritant

Hazard statements

  • H315Causes skin irritation.
  • H319Causes serious eye irritation.
  • H335May cause respiratory irritation.
Precautionary statements (16)
  • P261Avoid breathing dust, fume, gas, mist, vapours or spray.
  • P264Wash skin thoroughly after handling.
  • P264 + P265Wash skin thoroughly after handling. Do not touch eyes.
  • P271Use only outdoors or in a well-ventilated area.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P302 + P352If on skin: Wash with plenty of water.
  • P304 + P340If inhaled: Remove person to fresh air and keep comfortable for breathing.
  • P305 + P351 + P338If in eyes: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P319Get medical help if you feel unwell.
  • P321Specific treatment (see supplemental first aid instructions on the label).
  • P332 + P317If skin irritation occurs: Get medical help.
  • P337 + P317If eye irritation persists: Get medical help.
  • P362 + P364Take off contaminated clothing. And wash it before reuse.
  • P403 + P233Store in a well-ventilated place. Keep container tightly closed.
  • P405Store locked up.
  • P501Dispose of contents and container in accordance with local regulations.

GHS classification summary, not a safety data sheet (SDS). Classifications can differ by supplier, grade and concentration. Always check the supplier's SDS.

Full safety data and first aid

Phenol red suppliers

Sponsored listings first, then the documented ranking: membership, verification, replies, completeness, freshness and ratings

All 97 suppliers
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Where suppliers are based

97 suppliers in 14 countries

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Phenol red price

Indicative price range per kg from live supplier offers

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Uses and applications

What the substance is used for, by industry and function

Cosmetic ingredient, INCI name PHENOLSULFONPHTHALEIN(buffering)

Pharmacological actions

  • Coloring Agents
  • Indicators and Reagents

Roles

  • acid-base indicator
  • colour indicator
  • diagnostic agent
  • indicator
  • pharmaceutical
  • two-colour indicator
  • visual indicator

Functional uses

  • pH regulating agent

Cosmetic functions

  • Buffering

Regulatory status

Inventories, regulations and trade controls that list this substance

Health and food

  • EU cosmetic ingredient inventory

United States

  • TSCA inventory (USA)
    Status: Active in US commerce

HS code and trade data

Customs classification and reported world trade statistics

Global trade

World import and export statistics for the HS code Phenol red is traded under.

HS 2934.99Indicative HS code

Nucleic acids and their salts, other heterocyclic compounds, not elsewhere classified in heading 2934

World exports in 2024
$26.7B
+15.0% vs 2023, imports $26.3B
2019 to 2024
Top exporters
  1. Ireland26.3%
  2. China15.7%
  3. Singapore10.3%
Top importers
  1. United States24.5%
  2. Germany23.1%
  3. Japan4.5%
Reported customs values in USD, not prices.Full trade data

The HS code shown for Phenol red is indicative (it was assigned by structure rules). Confirm the classification with your customs broker before shipping.

Frequently asked questions

Quick answers about Phenol red, based on the data on this page

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.

What is the CAS number of Phenol red?

The CAS registry number of Phenol red is 143-74-8.

What is the molecular formula and weight of Phenol red?

The molecular formula of Phenol red is C19H14O5S and its molar mass is 354.38 g/mol.

What is Phenol red used for?

Known uses and roles of Phenol red include indicators and stains in research and laboratory, acid-base indicator, colour indicator, diagnostic agent, indicator and 7 more.

Is Phenol red hazardous?

Phenol red carries the GHS signal word "Warning". Main hazards: causes skin irritation, causes serious eye irritation, may cause respiratory irritation. This summary is not an SDS, always read the supplier safety data sheet.

What is the HS code of Phenol red?

Phenol red is usually classified under HS code 293499 (Nucleic acids and their salts, whether or not chemically defined, other heterocyclicโ€ฆ). This is indicative, confirm it with your customs broker before shipping.

Where can I buy Phenol red?

CompoundList lists 97 suppliers of Phenol red in China, United States, India, United Kingdom and 10 more. Send one free request to get and compare quotes. Your contact details stay private until you accept a quote.

Where can I buy Phenol red in India?

16 suppliers in India list Phenol red on CompoundList. Filter the suppliers list by country and send a request to compare prices, grades and delivery times.

What is the price of Phenol red?

Suppliers quote Phenol red on request because prices depend on grade, purity, quantity and destination. A free request on CompoundList gets you several quotes to compare.

Guides for buyers

Practical guides that help when you source, ship or handle Phenol red

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Data last updated 7 Oct 2026. Details may have changed, please confirm them with the supplier. Report an error on this page
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