SCIENCE PHOTO LIBRARY MOTION SCIENCE PHOTO LIBRARY MOTION
Universal indicator acid-base colour range. Footage of universal indicator solution being added to flasks containing liquids of different pH to demonstrate the range of colour changes used to identify acids and bases. The acid-base (pH) scale runs from 0 to 14. The central flask here displays a neutral pH (7), while liquids in the flasks at left are acidic and in the flasks at right are alkaline (basic). The colours and approximate pH values are, from left to right: red (pH 1), orange (pH 3), yellow (pH 5), light green (pH 7), dark green (pH 9), light purple (pH 12), and dark purple (pH 14). For the full ranges of colours after full mixing has occurred, see clip K005/3824.
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