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

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

44,794 views October 26, 2012 5:33

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Channel99Chemicals

Description from the creator

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!

About this tutorial

99Chemicals published this 5:33 video tutorial on October 26, 2012. It has been watched 44,794 times on YouTube.

Category
Education
Duration
5:33
Published
October 26, 2012
Views
44,794
Likes
166

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Further reading

  • How to build a red cabbage pH indicator - BBC Science Focus ... sciencefocus.com

    Blending the cabbage leaves with warm water is a quick way to extract this pigment by making it easier for it to dissolve in water. Anthocyanins change their colour depending on the pH of the solution they are in, which…

  • How to Make a Red Cabbage pH Indicator - ThoughtCo thoughtco.com

    You can make your own pH paper strips using a red cabbage indicator. Take filter paper (or coffee filter) and soak it in a concentrated red cabbage juice solution. After a few hours, remove the paper and allow it to dry…

  • Red Cabbage pH-indicator - University College London ucl.ac.uk

    Make your own pH-indicator, using red cabbage. For most pH indicators, the compound acquires a proton at low pH (lots of H +) but looses it at higher pH. This seemingly minor alteration is sufficient to alter the wavele…

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