Water What-ifs
Making Your Own pH Indicator

One recipe for red cabbage juice can be found at Beakman's World on the web at: http://www.beakman.com/acid/acid.html
A color scale is also provided.

Materials:

• head of red cabbage
• food processor or knife and cutting board
• saucepan (not aluminum) or 1000 ml beaker
• large glass container or 500 ml beaker
• storage jars
• sieve or tea strainer
• rubbing alcohol
• filter paper or coffee filter

Chop the red cabbage. Bring 2 cups of water (500 ml) to boil in saucepan. Add the cabbage to the boiling water and carefully remove from heat. Let the saucepan stand for 30 minutes. Strain the liquid-cabbage mixture and discard the cabbage. For storage, make a solution of the cabbage liquid and alcohol, using 1 part alcohol to 5 parts cabbage liquid. Label carefully to prevent accidents. The cabbage liquid can also be stored by freezing in ice cube trays.

To use as an indicator, add a drop or two of cabbage juice to the substance to be tested. Observe the color change. Another testing method is to soak a filter paper in cabbage liquid. Place on wax paper or paper plate to dry. Cut the dry paper into rectangular strips. The strips can be dipped into substances for testing.

References

The Science House. (1997.) Physics from the junk drawer / Counter top chemistry. Dubuque, IA: Kendall/Hunt Publishing Company.