The History of pH Paper

Written by eva david | 13/05/2017
The History of pH Paper
pH paper is used in chemistry to determine acidity. (chemical experiences image by Sergey Galushko from

The amount of acidity within a substance is a very important part of many scientific experiments. It is determined by a test conducted with pH paper. The paper changes colour when the substance is applied to it, indicating the level of acidity.


Measurement of pH, or the acidity or basicity of a solution, is crucial in many scientific experiments. It is the negative logarithm of the hydronium ion concentration. A high pH balance means a low concentration of ions, and a low pH means a high concentration. Compounds and solutions are mixed with the knowledge of the pH. It is uncertain what the "p" represents, but the "H" refers to hydrogen. The results of a pH test are applied to an internationally recognised pH scale.

pH scale

The pH scale was invented in 1909 by Soren Peder Pauritz Sorenson. He was a chemist at the Carlsberg Laboratory in Copenhagan, Denmark. The scale was known as the Sorenson scale until 1924, when it was revised and renamed. The pH scale ranges from 0 to 14, with the number 7 representing neutral pH. Neutral means it is neither acidic or basic. If the pH is less than 7, it is acidic. If it is higher than 7, it is basic.

Litmus Paper

Litmus paper is the most widely used type of pH paper. Schools generally use it for science and chemistry classes. When a solution is applied to the paper, it will change colour to reveal the level of pH found. The indicator litmus is red in acidic solutions (pH less than 7) and blue in alkaline (pH greater than 7) solutions.


The term "litmus" actually comes from Norse, meaning "to colour or dye." It is suspected that the pH paper was first invented in the early 1800s by a French chemist named J.L. Gay-Lussac. Lussac is more known for scientific laws he discovered involving gases and compounds. By noting naturally occurring pH indicators, such as pigments in certain plants, an idea for the paper was formed.


There are basic materials needed for the composition of pH or litmus paper. These are wood cellulose, lichens and adjunct compounds. The paper itself must be the purest possible so as to avoid misleading results. Because of this, the wood cellulose is treated with solvents prior to the manufacturing of the paper. The lichens are what give the paper its ability to detect acidic or basic properties. Lichens are a type of fungi.

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