Phenol Red CAS 143-74-8 PHENOL RED FREE ACID CELL CULTURE TESTED Phenolsulfonephthalein. Phenolsulfonphthalein

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Basic Info.
  • Brand Name: MOSINTER 
  • CAS No.: 143-74-8 
  • Molecular formula: C19H14O5S 
  • Molecular weight: 354.38 g/mol 
  • Density: 1.477g/cm3 
  • Melting Point: 300 °C 
  • Flashing point: 294.2°C 
  • Boiling point: 562.8°C at 760 mmHg 
  • Water solubility: 0.77 g/L 
  • Vapour pressure: 2.84E-13mmHg at 25°C 
  • Storage condition: Store at RT. 
  • Model No.: C19H14O5S 
  • Place of Origin: Shandong  
  • Min.Order: 1 Kilogram
  • Means of Transport: Ocean, Air, Land
Supply Capacity
  • Production Capacity: 50 Tons/year
  • Packing:According to the customer request
  • Delivery Date: within 7 days

Phenol Red (CAS: 143-74-8)





Red   crystal

PH indication range


Melting point ℃


Water solubility (g/l)


Residue on ignition (as sulfate) %

Basic information

Phenol red (also known as phenolsulfonphthalein or PSP) is a pH indicator that is frequently used in cell biologylaboratories.

Chemical property

Phenol red exists as a red crystal that is stable in air. Its solubility is 0.77 grams per liter (g/L) in water and 2.9 g/L in ethanol.It is a weak acid with pKa = 8.00 at 20 °C.

A solution of phenol red is used as a pH indicator: its color exhibits a gradual transition from yellow to red over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.

This solution contains a pH indicator which helps in monitoring of the pH changes in the cell culture. It will change from red to yellow color when the pH value decreases.

In crystalline form, and in solution under very acidic conditions (low pH), the compound exists as a zwitterion as in the structure shown above, with the sulfate group negatively charged, and the ketone group carrying an additional proton. This form is sometimes symbolically written as H2+PS− and is orange-red. If the pH is increased (pKa = 1.2), the proton from the ketone group is lost, resulting in the yellow negatively charged ion denoted as HPS. At still higher pH (pKa = 7.7), the phenol's hydroxide group loses its proton, resulting in the red ion denoted as PS2−.

In several sources, the structure of phenol red is shown with the sulfur atom being part of a cyclic group, similar to the structure of phenolphthalein. However, this cyclic structure could not be confirmed by X-ray crystallography.

Several indicators share a similar structure to phenol red, including bromothymol blue, thymol blue, bromocresol purple,thymolphthalein, and phenolphthalein. (A table of other common chemical indicators is available in the article on pH indicators.)

Drug instructions

1.Character:This product is a red transparent liquid

2.Check the pH:Should be 6.5 ~8.5

storage :Airtight save

Pharmaceutical analysis

Determination of phenol sulfonic phthalein - neutralization titration:

applied range:This method USES the titration method to determine the content of phenol sulfonic phthalein.

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