Litmus Paper

What Is Litmus Paper?

A type of paper that changes colour in response to the acidity of the solution it is dipped in and can thus be used to measure acidity.

Litmus paper is a filter paper that has been treated with a lichen-provided natural-soluble dye. Litmus paper is a piece of paper that produces a result which can be used as a pH indicator.

Litmus is mainly used to assess whether a solution is acidic or basic. The colour transition occurs over the pH range 4.5–8.3 at 25 °C (77 °F), with light blue litmus paper turning red under acidic conditions and red litmus paper turning blue under basic or alkaline conditions. Purple litmus paper is neutral.

Table of Contents

• • Recommended Videos
  • History of Litmus Paper
  • Litmus Paper Experiment
  • Litmus Paper Test for Acid and Base
  • Frequently Asked Questions – FAQs

Recommended Videos

History of Litmus Paper

Arnaldus de Villa Nova, a Spanish physician, used litmus for the first time around 1300. The blue dye was extracted from some lichens from the 16th century onwards, especially in the Netherlands.

Wood cellulose, lichens, and adjunct compounds are the primary raw materials used to produce litmus paper. Litmus paper is made mainly of paper, as the name suggests. Litmus paper must be free of pollutants that could influence the pH of the system being tested.

Lichens are used to make litmus. In distilled water, it has a mauve (purple) tint. It turns red when added to an acidic solution and blue when added to a basic solution. As a result, it’s used to determine whether a solution is acidic or basic.

Litmus Paper Experiment

Litmus paper or red and blue test strips can tell you whether a solution is acidic or basic, but they can’t tell you how strong the solution is. Every number on the pH scale is represented by a different colour on a universal indicator. The paper turns green when neutral solutions are used.

When deciding whether a solution is acidic or basic, litmus paper is used. Litmus paper does not have correct details about the acid or base power. Litmus paper is filter paper that has been treated with a lichen-derived natural water-soluble dye. Litmus paper, as a result of the process, may be used as a pH indicator. 

Procedure:

• • • • To measure at least nine substances, tear each piece of litmus paper into three smaller parts.
      • Take one small piece of red litmus paper and fold it in half. It should be dipped into one of the substances that will be checked. Using a small piece of blue litmus paper, repeat the procedure.

If the blue Litmus paper turns red and the red Litmus paper remains untouched, the material is acidic. If the red Litmus paper turns blue and the blue Litmus paper remains untouched, the material is alkaline. The material is neutral if neither the red nor the blue paper changes colour.

Litmus Paper Test for Acid and Base

Count the hydrogens on each material before and after the reaction to decide if it is an acid or a base. The substance is acid if the number of hydrogens has decreased (donates hydrogen ions). The substance is the base if the number of hydrogens has increased (accepts hydrogen ions).

A litmus test is used in chemistry to determine if a solution is acidic or basic. During a litmus exam, a special type of paper is dipped in the liquid being examined. The material is tested using litmus paper, which turns red if it’s acidic and blue if it’s alkaline, or basic.

Litmus paper is red when the pH is less than 4.5 and blue when the pH is greater than 8.3. If the paper turns purple, the pH level is close to neutral. The sample is an acid if the red paper does not change colour. The sample is a base if the blue paper does not change colour.

Litmus paper is divided into two categories: red litmus paper and blue litmus paper. If the material is acidic, the blue litmus paper turns red. If the material is basic or alkaline, the red litmus paper turns blue. In acidic solutions, litmus turns red, while in simple solutions, it turns blue.