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Old 04-08-2006, 10:43 PM
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I think you're a bit confused, so here's something more to make it easier....

Red cabbage contains a pigment molecule called flavin (an anthocyanin). This water-soluble pigment is also found in apple skin, plums, poppies, cornflowers, and grapes. Very acidic solutions will turn anthocyanin a red color. Neutral solutions result in a purplish color. Basic solutions appear in greenish-yellow. Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice.

The color of the juice changes in response to changes in its hydrogen ion concentration. pH is the -log[H+]. Acids will donate hydrogen ions in an aqueous solution and have a low pH (pH < 7). Bases accept hydrogen ions and have a high pH (pH > 7).

Here is a table of approximate colors of red cabbage indicator solution at different pH's. If you wish, make your own chart, using chemicals of known pH.
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The Newtons and friends were taking tea
Beneath the boughs of an apple tree,
When a falling fruit landed on the
Head of the head of the family.
Mrs. Newton cried, 'Well deary me!
That could've caused an injury'.
But clever Isaac alone could see,
The situation's true gravity.

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