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How to Make a Red Cabbage pH Indicator (Extraction of Anthocyanins)





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Uploaded on Nov 20, 2011

In this video I will show you how to make a red cabbage pH indicator. This is a very interesting experiment that is very simple.

What you will need:
Red cabbage
Distilled water (Reverse osmosis will work too)
A stove or heat source

First cut the cabbage leaves into small pieces and add them to distilled water and bring to a boil, let it boil for 2 minutes and then turn off heating and let cool slowly.

Now you have your indicator and some cabbage pieces. Use a strainer or coffee filter to remove particles.

The deep purple solution is your indicator you can refrigerate it for short term use or add 15% volume of alcohol (im using 91% isopropanol)

You can test the indicator by adding acids and bases.
In an acid environment it turns red (NaHSO4, HCl, Citic acid etc...)
In a neutral environment its purple (Distiled H2O)
In mild bases it is blue (Sodium Acetate)
In weak bases it is blue green (NaHCO3)
I medium strong bases it is dark green (Na2CO3)
In very strong bases it is yellow (NaOH)

The active chemical in the indicator is Anthocyanins. They change color in acid and basic environments. Red cabbage is high in Anthocyanins but other plants like raspberrys, grapes, and purple corn have similar chemicals that change color in pH.

Thanks for watching!


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