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Universal indicator colour range. Inverted burette containing a recently mixed combination of an acid, an alkali and universal indicator. The range of colours indicate the variation in the hydrogen ion concentration (pH values). At bottom the pink colour indicates a strong acid (pH<1), with acidity decreasing toward the centre. The central colour band of yellow is neutral (pH=7). Moving towards top, the alkalinity increases until its maximum at pH=14 (dark brown).
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