How to read a litmus test paper

Written by marc wright
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How to read a litmus test paper
Litmus paper is used to measure the acidity or alkalinity of a solution. (Ann Cutting/Brand X Pictures/Getty Images)

Litmus paper is used to identify whether a chemical solution is acidic, alkaline or neutral. Different litmus papers are used to test different things. Red litmus paper, for example, is used to test the base of a solution. Blue litmus paper is used to test the acidity of a solution, and a neutral litmus paper will change colour to indicate an acid or alkaline accordingly. A pH scale is used to interpret the results of a litmus paper reading.

Skill level:
Moderately Easy

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Things you need

  • Litmus paper
  • Solution
  • pH scale

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Instructions

  1. 1

    Choose the appropriate type of litmus paper. If you are checking for acidity, use blue litmus paper. Use red litmus paper to test for a base and neutral paper to determine a solution's pH.

  2. 2

    Dip the litmus paper into the solution. The solution should reach halfway up the paper to give a clear reading.

  3. 3

    Remove the paper from the solution and hold it between your fingers. Wait for the paper to change colour.

  4. 4

    Record the colour change of the litmus paper. If the blue paper turns red, then the solution is acidic. If the red paper turns blue, then a base is present in the solution. If you are using neutral litmus paper, refer to the pH scale.

  5. 5

    Look at the pH scale. Match the change in colour of your litmus paper to the appropriate colour on the scale. Record your results.

Tips and warnings

  • Solutions make the paper wet, which gives the appearance of a darker colour. This may cause you to misinterpret the test. Double-check by testing the solution with blue and red litmus paper. If there is no obvious change in colour, then the solution does not contain acid or a base.

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