|Posted on November 18, 2018 at 6:50 PM|
An incredibly versatile and delicious herb, turmeric has been for at least four or five thousand years. Its use has been documented since ancient times as a culinary herb for color and flavor, cloth and food dye, paint, medicine, and so much more! A staple in Indian and southeast Asian cooking, turmeric has even become a favorite in many parts of the U.S. for its deep color and rich flavor. Would you have guessed that something so multi-purpose could even be used in chemistry as well?
Just like many other natural substances such as red cabbage juice or horse chestnut leaves, turmeric is a natural pH indicator. This means it changes color depending on pH exposure. While red cabbage juice uses a wide variety of chemicals to do this, and horse chestnuts use Esculin, turmeric uses a yellow pigment called curcumin. When curcumin is exposed to a basic substance or solution, it changes color from yellow to a deep red. Before we get into any experiments, though, we need to make sure we know about the pH scale.
The general pH scale goes from 0-14. At the zero end are acids. To put it simply, acids are chemicals that neutralize alkalis and may dissolve some metals. In advanced terms, an acid can donate a proton or accept an electron pair in reactions. At the other end of the scale are bases. Simply, bases neutralize acids and may corrode some organic or inorganic materials. In advanced terms, a base donates electrons or hydroxide ions, or accepts protons. Right in the middle of those two is neutrality. Neutral substances are neither an acid or a base, and have a pH of around 8. We have acids and bases all over our home, from the vinegar we use in our food to the soap we wash ourselves with, pretty much everything falls somewhere on the pH scale. Let’s see how acids and bases react with a turmeric indicator!
What you will need:
-1 tablespoon Turmeric
-1 cup 91% isopropyl rubbing alcohol
-Some acidic and basic substances to experiment with, such as lemon juice and soapy water
-Glass jars or other glass containers
What to do:
Are you wearing protective gear? If not, be sure to put some on!
First, we need to make our indicator by extracting the pigment from the turmeric. In order to do this, mix the rubbing alcohol and turmeric and stir well. You may even want to give it a heavy shake. Let it the mixture steep for 10 minutes, stirring occasionally. Once the liquid seems to have a nice yellow color, let the mixture rest for another five minutes, to allow the turmeric particles to settle to the bottom. Once settled, pour the liquid two clean containers, making sure not to pour any of the turmeric particles from the bottom over. Now you have a turmeric indicator solution!
In one indicator, try adding something acidic (i.e. lemon juice or vinegar). Did you notice any change? Now, try adding something basic to the other indicator (i.e. soapy water). Did you notice a change this time? As the pigment in turmeric reacts to bases, you should have noticed the color of the solution go from bright yellow to a deep red. Next, try adding some acidic substance to the changed indicator. It should change right back to yellow again! It might look like magic, but it’s really science!
Project notes: For our experiment, we used soapy water as the base and pool chemicals as our acid. You can always make more indicator and experiment with different substances around the home. Just keep in mind that while acids and bases mostly neutralize each other, some substances may react in a dangerous or hazardous manner. Make sure the substances you mix are safe and non-reactive.
Did your indicator react to the base? What kinds of acids and bases did you use? Let us know in the comments section below or share it with us on Facebook, Twitter, or Instagram! Not only does it help others undertaking this experiment, but we love to see how your projects turn out!
CJ w/ Children of Terra-NEO
https://www.ncbi.nlm.nih.gov/books/NBK92752/" target="_blank">National Center for Biotechnology Information-Turmeric, the Golden Spice
https://www.thoughtco.com/home-and-garden-ph-indicators-601971" target="_blank">Thoughtco-Home and Garden pH Indicators
https://www.thoughtco.com/definition-of-base-604382" target="_blank">Thoughtco-Definition of a Base
https://www.chemicool.com/definition/acids.html" target="_blank">Chemicool Dictionary-Definition of an Acid