Neutral Litmus Paper and How You Can Make Substances Neutral with Vinegar and Soap
Neutral litmus paper can occur when the paper is dipped in a substance which is neither acidic or basic. For example, water is a neutral substance as it is neither acidic or basic. Neutral litmus paper usually has a grey/purple colour until it is dipped in an acid or base. There are other experiments you can do to achieve neutrality by neutralising two substances, an acid and a base.
Try the following experiment below. It shows you how to make litmus paper and how to make it neutral.
How to Make your pH Litmus Test Strips
- Making your litmus test strips is easy and can be made using household ingredients. You can use all sorts of flowers and vegetables to make them. The easiest to find and buy is red cabbage. It contains a pH indicator. You may notice it's purple in the shop, if you wash it with tap water it goes blues and it goes red if you spill vinegar on it. This is because tap water is slightly basic so it will turn the red cabbage blue and vinegar is acidic so it will turn the cabbage red. This concept can also be applied to our litmus test strips. Here are the steps below:
- Chop about half to two-thirds of a red cabbage. Put it in a bowl and pour boiling water over it.
- Leave it there for twenty to thirty minutes. You will notice after a while that the purple-coloured dye is coming out from the cabbage and into the water. The more concentrate it is, the better.
- Strain the cabbage from the purple-coloured solution
- Cut strips of blotting paper and place them into the purple coloured solution. Leave them there for a few minutes to soak.
- Take them out and leave to dry.
That's it! Now that you have your strips you can now see which substances are neutral and which are not.
Time to Test for Neutral Substances
Dip your paper into water or milk. You will notice that the strips stay the same colour. That means that the substances you have tested are neutral. If you dip your strips into vinegar or lemon juice, the strips will turn red. This is because they are acidic. If you dipped the strips into milk of magnesia it will turn blue/green. Milk of Magnesia is a basic substance.
Here are other substances you could test to see whether they are neutral or not:
Substances you could test
Is your rainwater neutral?
Rainwater these days is slightly acidic. This is caused by carbon dioxide being released from factories and cars. These gases travel up into the sky and mix with the clouds. A weak carbonic acid is formed. Then the acid rain falls damaging limestone and killing fish. This is very harsh to the environment and is very severe in some countries.
You can test whether there is acid rain in your area. Here is the experiment:
- Place a glass jar with a funnel outside away from any shelter.
- Leave there until it rains.
- After it rains, dip a strip of your litmus strips into the rainwater. Chances are it will be slightly acidic. If not, if it's neutral, well done! The air around you must be very pure!
Neutral Litmus Paper and Achieving Neutrality
Here is an experiment to try make your litmus paper neutral after dipping it in vinegar.
- Dip your litmus paper into vinegar. It will turn it red, naturally. Then add the same amount of washing up liquid into the vinegar. Dip another strip in, this time the strip won't change colour at all! This is because the washing-up liquid (base) neutralised the vinegar.
- You could try this with other substances. For example:
- Lemon juice with toothpaste
- Baking Soda with lemon juice
Universal Indicator Paper
Litmus paper only tells you whether a substance is an acid or a base. In most laboratories, scientists need to know how strong the acid they are using really is. So they use universal indicator paper. It goes a different colour depending how strong an acid or a base is on the pH scale.
Give Your Say!
Would you like to make litmus paper?
I hope you have enjoyed this article. Please feel free to add any comments below.