Products / pH Indicators


C.A.S. No. 143-74-8
M.F. C19H14O5S
M.W. 354.38gm/mole


Dye Content (by Spectrophotometry) >95%
Solubility 0.1 % (95% EtOH) Clear solution
Transition range pH 6.5-8.2
Yellow-Reddish violet
Absorption Maximum (pH 6.5) ?1max 430-435nm
Absorption maximum (pH 8.2) ?2max 557-560nm
Absorptivity (A1%/1cm at pH 6.5 at ?1max) 600-700
Absorptivity (A1%/1cm at pH 8.2 at ?2max) 1100-1200
Loss on drying (110°C) <1%

Chemical Name


InChI Key


Product Description

Phenol red is a water-soluble dye used as a pH indicator, changing from yellow to red over pH 6.6 to 8.0, and then turning a bright pink color above pH 8.1. As such, phenol red can be used as a pH indicator dye in various medical and cell biology tests.


Practically insoluble in chloroform, ether. Soluble in aqueous alkali hydroxides or carbonates with red color (removed by boiling with zinc dust).
Solubility in water: approximately 1g/1300ml.
Solubility in alcohol: approximately 1g/350ml
Storage and Shelf Life : Store between 10- 30°C. Use before expiry date on the label.


Chemicals and substances that impart color including soluble dyes and insoluble pigments. They are used in INKS; PAINTS; and as INDICATORS AND REAGENTS.Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents.

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