About Acid-Base Indicators

 
To make an acid-base indicator:

1. Finely chop half a head of red cabbage.
    
2. Carefully boil the chopped cabbage in about a liter of water for 5 minutes.
    
3. Remove from heat and let stand until completely cool.
    
4. Strain the liquid, and throw away the cabbage.
    
5. The liquid should be a dark reddish-purple color.

   This is the organic compound that acts as an acid-base indicator.

 

Test your indicator with the following:

• A colorless neutral solution like water.

  Only "de-ionized" water is exactly neutral. But most tapwater is close to neutral.

• A colorless base solution like household ammonia.
   
• A colorless acid solution like vinegar.

 
To make an "A" on this lab, bring the following to class:

• A small amount of your indicator.
   
• A piece of paper with the results of testing the indicator.