How to Use Litmus Papers

Every high school science student has probably been faced with those little strips of paper and asked to tell if something is a base or an acid. Litmus paper comes in three kinds, though the most common are the red ones and the blue ones. Using them is very easy to do, and perfect for testing out the acidity/alkali nature of common chemicals such as lemon juice or bleach (a common school science experiment). For more complex studies, a Ph strip similar to litmus is often used.

Things You'll Need

• Litmus paper, either red and blue, or purple
• Safety gear: gloves, apron or lab coat, gloves
• Wide-mouthed glass beaker for chemical solutions

Instructions

1. 

   Pour a small amount of the chemical to be tested into a wide-mouthed beaker. There only needs to be enough to dip the end of the paper into the liquid.

2. 

   Take one strip of blue litmus paper and dip the end into the chemical to be tested. The paper does not need to soak, simply getting it wet will be enough.

3. If the blue litmus paper turns red where you have tested it, the chemical is an acid. If there is no reaction then it is not and you can move on to testing the chemical with the red litmus paper.

4. 

   Take one strip of red litmus paper and dip the end into the chemical to be tested. As before, the paper does not need to soak, simply getting it wet will be enough.

5. If the red litmus paper turns blue where you have tested it, the chemical is a base. If there is no reaction to either the red paper or the blue paper, then the substance has a neutral Ph and is neither an acid nor a base.

Tips & Warnings

• There is also a purple, or neutral litmus paper. This paper turns red in the presence of an acid or blue in the presence of a base. Simply follow steps 1 through 3 above. For more complex studies, a Ph strip similar to litmus is often used. These come with a color-coded chart.

• Some household substances can be harmful if they come into contact with skin, others can stain clothes and furniture. Be sure to have on the proper safety gear and work in a safe and stable location. Minors should be supervised t all times when handling any chemical.

Resources

• Litmus Paper Lesson Plan