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Cresol Red

Cresol Red

Identifiers
CAS number	1733-12-6
SMILES	Cc1cc(ccc1O)/C(=C/2C=CC(=O)C(=C2)C)c3ccccc3OS(O)=O
Properties
Molecular formula	C₂₁H₁₇NaO₅S
Molar mass	404.41 g/mol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Cresol Red (pH indicator)
below pH 7.2		above pH 8.8
7.2	↔	8.8

Cresol Red (full name: o-Cresolsulfonephthalein) is a triarylmethane dye frequently used for monitoring the pH in aquaria.

Additional recommended knowledge

Recognize and detect the effects of electrostatic charges on your balance

What is the Correct Way to Check Repeatability in Balances?

How to quickly check pipettes?

Cresol Red can be used in many molecular reactions instead of water. For example restriction digestion or PCR.

Cresol Red can also be used as a color marker to monitor the process of agarose gel electrophoresis and polyacrylamide gel electrophoresis. In a 1% agarose gel it runs approximately at the size of a 125 base pair (bp) DNA molecule (it depends on the concentration of buffer and other component). Bromophenol blue and xylene cyanol can also be used for this purpose.