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: