- Finely chop half a head of red cabbage.
- Carefully boil the chopped cabbage in about a liter of water for 5 minutes.
- Remove from heat and let stand until completely cool.
- Strain the liquid, and throw away the cabbage.
- The liquid should be a dark reddish-purple color. This is the organic compound that acts as an acid-base indicator.
Test of your indicator by adding a few drops to:
- A colorless neutral solution, like water. (Only de-ionized water is exactly neutral, but most tapwater is close enough for this test.)
- A colorless base solution, like household ammonia.
- A colorless acid solution, like distilled vinegar.
To make 100% on this lab, bring the following to class:
- A small amount of your indicator.
- This lab report guide showing the results of your indicator test.