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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

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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.