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Endpoint in titration experiment. Close-up footage of a demonstration of the end point of an acid-base titration using the indicator phenolphthalein. A solution of hydrochloric acid is in the flask, with a few drops of the indicator added. Sodium hydroxide solution (a base) has been added from a burette (not seen). When the mixture in the flask approaches its end point (when the acid and base are exactly neutralised), adding further amounts of base turns the solution alkaline. This causes the indicator to show as purple, even after swirling, as seen here.
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