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 |