How to Test Home Water pH Using Cabbage

Ever have the need to test pH of your home water, aquarium, pool, etc... But you don't want to spend a load of cash on the fancy testing chemicals? Well, there is a way to do it for about a dollar.
Believe it or not, red cabbage is a natural source of a type of Anthocyanin called Flavin that changes colors in different concentration of hydrogen ions. What does this mean? It is a natural pH indicator!
Anthocyanins are natrually occuring anti-oxidants that are found in grapes, apples, and almost every fruit. However, a specific one called Flavin found in red cabbage is what we are interested in.

Difficulty: Easy

Instructions

Things You'll Need:

• Red Cabbge
• Pot
• Spaghetti Strainer
• Stove
• Distilled Water (Not just filtered)

1. The first step is to chop up your head of read cabbage into tiny pieces about a centimeter (1/4") in size. Be sure to use a fresh head of red cabbage from the market, not a can or jar of pickled cabbage.

2. Once you have the cabbage chopped up, dump the entire pile into a clean pot on the stove, and pour in enough distilled water to submerge about 80% of the pile. Be sure to use distilled water, and nothing from your tap. Since we want to test the pH of your home's water, we must be sure the water we are using to make the indicator is as neutral as possible.

3. Bring the solution to a boil while stirring the cabbage. Allow the water to boil for at least ten minutes while stirring, and then continue boiling until about 1/2 of the original water is evaporated. This will maximize the concentration of Flavin in the water. The water should be a deep violet color, this means you have successfully extraced the Flavin from the Cabbage!

4. Pour the water through a spaghetti strainer to remove the cabbage chunks. If a few small chunks are left, it will not affect the pH testing. Put the solution into a jar or bottle to store it. You can use it over and over, pouring out small amounts for each test.

5. 
    
   Here is what each pH looks like with red cabbage indicator

   To test the pH of some water, fill a glass with the water you wish to test (from your tap for example). And then poor in a small amount of the indicator. It does not matter how much you want to put in. Pour in just enough to tell what color it is. This will maximize the usage of the indicator you made.
   Use the following scale to see what the pH of the water is:
   Red = 2 or lower
   Purple = 3 to 4
   Violet = 5 to 6
   Blue = 7 to 8 (neutral)
   Aqua = 9
   Green = 10
   Yellow = 11+

6. Ideally you want your tap water as close to neautral as possible. It is very difficult to have a pH of 7, and any glass of water sitting out in open air will be acidic. This is because CO2 from the atmosphere is absorbed into the water and chemically changed into Carbonic acid (H2CO3), the same acid in soda pop.
   
   It is fun to experiment with different household chemicals to see the color change. Keep in mind it is best to use chemicals that are clear! Otherwise it will change the color of the indicator. Try putting it in distilled vinegar, it should change to a deep red. If you put it in bleach or ammonia, it will change it all the way to yellow (basic)

Tips & Warnings

• You can also soak strips of coffee filter in the indicator over night and then dry them. This will give you home made pH testing strips you can safely put in your aquarium!

[KRLawrence]

on 1/15/2009 Really cool... I will share with my son's science teacher