Phenolphthalein in a labelled reagent bottle. This colourless chemical (formula: ) is used as an indicator for acids and bases. The ion that

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Phenolphthalein in a labelled reagent bottle. This colourless chemical (formula: ) is used as an indicator for acids and bases. The ion that forms with decreasing acidity is pink. This colour change occurs around pH 9, and is used to indicate acid neutralisation of an alkali during titration experiments. The current UN Globally Harmonized System of Classification and Labelling of Chemicals [GHS] labels indicate that this chemical is flammable and harmful to health. As well as the symbols there is a signal word and suppliers provide numbered statements H225, H341 & H350 that give more information.

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