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Edible Indicators

Summary

The anthocyanin in cabbage is used to demonstrate pH differences in household chemicals.

Materials

  • Purple Cabbage (other fruits & vegetables which work well are radishes, beets, blueberries, grape juice. Note: Purple cabbage offers a wide range of colors and is probably the best example if a single indicator is to be used)
  • Beakers/cylinders
  • blender
  • array of buffers pH 2-13
  • household items
    • vinegar
    • aspirin
    • baking powder
    • ammonia

Procedure

  • To make cabbage indicator simply place several cabbage leaves in a blender, add water and puree.
  • Add indicator to each cylinder in the array of buffers.
  • The pH of household chemicals can be tested by adding indicator and comparing the color produced to the buffer array.

Note: The indicators tend to deteriorate on standing and should be either freshly prepared or refrigerated if necessary for a day or two. I have frozen them in ice cube trays and they have kept well for several weeks. The indicator is an anthocyanin.

Discussion

For cabbage:

pH Color Compound
1-3 pink 7-up, vinegar, asprin, lemon juice
4-7 purple tap water
8 blue soap
9 blue green
10 green sodium bicarbonate, Rolaids
11 green-yellow
12 & up yellow ammonia, drano
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