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Chemistry > Acid Base Indicators

The table below shows the most common acid base indicators and standard pH ranges. Some may not be available to purchase in this country and are included for reference only. Indicators may vary in pH range, but this will be indicated on the packaging or in supplier's catalogues. If in doubt, refer back to the manufacturer.

Indicator pH Range Acid Base
Thymol Blue 1.2 - 2.8 red yellow
Pentamethoxy red 1.2 - 2.3 red - violet colorless
Tropeolin OO 1.3 - 3.2 red yellow
2,4 - Dinitrophenol 2.4 - 4.0 colorless yellow
Methyl yellow 2.9 - 4.0 red yellow
Methyl orange 3.1 - 4.4 red orange
Bromphenol blue 3.0 - 4.6 yellow blue - violet
Tetrabromphenol blue 3.0 - 4.6 yellow blue
Alizarin sodium sulfonate 3.7 - 5.2 yellow violet
α - Naphthyl red 3.7 - 5.0 red yellow
p - Ethoxychrysoidine 3.5 - 5.5 red yellow
Bromcresol green 4.0 - 5.6 yellow blue
Methyl red 4.4 - 6.2 red yellow
Bromcresol purple 5.2 - 6.8 yellow purple
Chlorphenol red 5.4 - 6.8 yellow red
Bromphenol blue 6.2 - 7.6 yellow blue
p - Nitrophenol 5.0 - 7.0 colorless yellow
Azolitmin 5.0 - 8.0 red blue
Phenol red 6.4 - 8.0 yellow red
Neutral red 6.8 - 8.0 red yellow
Rosolic acid 6.8 - 8.0 yellow red
Cresol red 7.2 - 8.8 yellow red
α - Naphtholphthalein 7.3 - 8.7 rose green
Tropeolin OOO 7.6 - 8.9 yellow rose - red
Thymol blue 8.0 - 9.6 yellow blue
Phenolphthalein 8.0 - 10.0 colorless red
α - Naphtholbenzein 9.0 - 11.0 yellow blue
Thymolphthalein 9.4 - 10.6 colorless blue
Nile blue 10.1 - 11.1 blue red
Alizarin yellow 10.0 - 12.0 yellow lilac
Salicyl yellow 10.0 - 12.0 yellow orange - brown
Diazo violet 10.1 - 12.0 yellow violet
Tropeolin O 11.0 - 13.0 yellow orange - brown
Nitramine 11.0 - 13.0 colorless orange - brown
Poirrier's blue 11.0 - 13.0 blue violet - pink
Trinitrobenzoic acid 12.0 - 13.4 colorless orange - red

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