How to Make a Red Cabbage pH Indicator

Red Cabbage extract changes color in acid and base solutions.

Scientific name: Anthocyanin works like a natural pH-indicator.

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Safety

Wear eye protection goggles and gloves.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

anthocyanin (violet) -[pH change]→ anthocyanin (colored)

Step-by-step instruction

  1. In this experiment the pH indicator from red cabbage is obtained. The first way to prepare it is by extraction of compounds from red cabbage leaves.
  2. Boil some water (about 100 ml) and add a few pieces of red cabbage. The more red cabbage is used the more concentrated indicator solution will be obtained.
  3. Let it boil for about 5-10 minutes until the water becomes colored.
  4. Filter out the leaves.
  5. Cool down the solution.
  6. The second way is to grind red cabbage leaves and separate the obtained liquid. Put the plant material into a blender and add some water. Blend it for a while and then filter it.
  7. When the indicator is ready you can test it on some household substances. For example: vinegar, baking soda solution, water solution of ammonia, lye, lemon juice.
  8. Pour the liquid under study into a glass and add some red cabbage indicator. It will change the solution color depending on hydrogen ion concentration in it.

Scientific background

Red cabbage contains anthocyanin. This substance could be used as pH indicator. In acidic solutions it becomes red, in neutral – purple and turns alkaline solutions green. This property of red cabbage allows using its extract to find out whether the liquid under study acidic or alkaline.

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Published on 30 March 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst