my next pH test kit

[wui39]

Interesting link I found on how cabbage can be used as an indicator

For Those of You Who Can't Afford a pH Test Kit

Chop a red caggage in half twice. Throw one of the red cabbage chunks into a blender filled with water. Turn the blender on high for a minute or two until the water turns purple. Use a strainer to remove the tiny pieces of red cabbage. This purple cabbage juice is an acid base indicator. You can use it to test all kinds of household products such as lemon juice, baking soda and vinegar. If you add an acidic liquid, it will turn the cabbage juice indicator pink. If you add an alkaline liquid, it will turn to an aqua-green color.

Why does it work? The red cabbage juice is made of molecules. A molecule is a group of atoms that are linked together. Hydrogen, Carbon, and Oxygen are the most common atoms that make up molecules in fruits and vegetables,such as red cabbage. Many molecules change their structure slightly, depending on whether they are in an acid or a base solution. Red Cabbage juice contains these changing molecules. This change in their structure changes their color. Molecules that change color when they are in different solutions may be used as indicators.

The purple color of the cabbage is due to the way light is absorbed by or bounces back from molecules in the cabbage. Small changes in the shape of a molecule can change the way light bounces off or is absorbed by the cabbage. When a chemical reaction occurs (ie- acid or base is added to the cabbage juice), these molecules change, causing the color of the indicator to change.

Credit goes to panaque from www.plecofanatics.com

Is this how they make real pH test kits

[mianos]

A bit more of a technical description is at:

http://chemistry.about.com/library/weekly/aa012803a.htm

This one is no urban myth, cabbage contains, aside from molecules (loved that bit ), anthocyanin which actually does change colour depending on pH.

[wui39]

Wonder what the lifespan on the solution is.....the strips of filter paper with the solution seem to be a good idea though.

[D6C1]

This takes me back to my chemistry days in high school!