The pH or hydrogen potential of a solution is a relevant variable when it comes to determining the quality of water, whether it is a drink or an aquatic environment. There are several proprietary commercial tools of varying complexity and precision to measure this parameter. However, for this activity we intend to use natural pigments that are sensitive to this parameter and thus be able to measure pH with elements that are available to anyone.
An environmental friendly method exist for pH determination of water samples. The Brasica oleracea cabage has high concentration of anthocyanins pigments that are sensitive to pH changes of a solution. This fact has been documented in several reseach papers that explore it potencial:
Determine the pH of different samples with pigments extracted from purple cabbage (Brassica oleracea).
Necessary materials 📝
- A cup of chopped purple cabbage
- A cup of distilled water
- A clean pan
- Clean glass containers
- Samples of liquids of known pH (vinegar, sodium bicarbonate solution, bleach, laundry soap, carbonated cola drink).
- Sample of water that you are interested in knowing its pH. It can be from a nearby river or lake.
All steps in one
There is a YouTube link
Step 1 🔪
Cut the cabbage into small pieces with a knife to fill a cup
Step 2 🔥🔥🔥
Put the chopped cabbage with a cup of water in the saucepan and simmer for 15 minutes
Step 3 ❄️
Filter the liquid from the pot and let it rest until cool
Step 4 💧 ❓
Try different substances to find out their pH values. The image below indicates the equivalence between different colors and pH values.
Making an indicator from red cabagge 🌈 by Andy Brunning / compoundchem.com; under licence CC BY-NC-ND 2.0
The test tubes above correspond to hydrochloric acid (dangerous), river water, sodium bicarbonate solution, carbonated cola drink and alcohol vinegar. Original picture
Step 6 📷
Share your photos with the PublicLab community and social media!!!
Knowing as much as we can about the aquatic environments that care us is key to being able to detect any negative effects on them in time.
Clarification: that the pH value of an environment is at normal values does not mean that this environment is not suffering some kind of disturbance, to determine that an environment is in optimal conditions requires a integrative analysis of it.