Litmus, What Is It? and Why Is It Important?

Litmus, what is it? And why is it important? Litmus was first used around 1300 AD by Arnaldus de Villa Nova, a Spanish alchemist . The word Litmus, comes from the Norse word, meaning ‘to dye, or color’ . Litmus is a common acid-base indicator. Acid-base indicators are indicators used in chemistry as chemical detectors. They provide information about changes in the environment. They are widely used in chemistry due to the fact that they change color reversibly, indirectly indicating the concentration of hydrogen ions present in tested solutions or mixtures.

Being one of the most well known acid-base indicators, litmus is a water-soluble mixture of different dyes derived from natural substances, lichens, especially Roccella tinctoria, which is a kind of composite organism consisting of symbiotic association of a fungus with a photosynthetic partner, most commonly green algae . Litmus can be in a dark blue aqueous form, and it can also be absorbed onto filter paper to become the most common and oldest form of pH indicator.

Neutral litmus paper is purple in color In the presence of acids, blue litmus paper turns pink; In the presence of alkalis, red litmus paper it turns blue.

Hence, it is often used for testing for the presence of acids and alkalis. This color change occurs over the pH range of 4. 5 – 8. 3 at 25°C. Litmus itself is a weak acid , when it is un-ionized it is red, when it is ionized, it is blue. If litmus is added to a solution where there is a presence of hydroxide ions, the hydroxide ions will react with the hydrogen ions from litmus, the equilibrium position moves to replace the lost hydrogen ions, hence litmus turns blue.

Similarly, when it is added into a hydrogen ion containing solution, there will be extra hydrogen ions and so the equilibrium will shift in the other direction, to remove the extra hydrogen ions present, hence litmus turns red. When the concentration of hydrogen ions and unionized limus is the same, a position of equilibrium is reached and the neutral state will be shown by the color purple, a mixture of red and blue. Having many uses in the science field, litmus is certainly an important indicator.

It can be used in various fields of science, such as and not limited to, chemistry, biology, and botany. In chemistry, it is most recognized as an indicator used for determining whether substances are basic or acidic. It can also indicate end points during experiments involving titrations. Litmus paper is also very commonly used by chemistry teachers to teach topics related to acids and bases. In biology, litmus paper can be utilized to test specific environmental and biological factors, testing the pH levels.

Knowing the pH of the environment is of high importance in this field as most life forms can only survive in a very small range of pH levels. For example, with homo sapiens, humans, the pH levels in their blood have to be very constant, slight changes like blood carbon dioxide levels can easily result in serious damage, coma and may even lead to death. An example of pH testing in this field is the pregnancy test, where the urine acidity of subjects can indicate whether or not they are pregnant.

In the field of botany, which is the scientific study of plants , litmus can be used in testing the pH of soil. Plants can only grow in soil of some ranges of pH, if soil is too acidic, they cannot grow or develop properly. If the pH is not right, fertilizers composed of basic components such as calcium carbonate can be used to help foster plant growth. To conclude, litmus is an acid-base indicator with a long history of use in many fields of science and has much importance in those fields.

http://chemistry.about.com/b/2009/01/09/what-is-litmus-paper.htm

http://www.ehow.com/about_5061005_uses-litmus-paper.html

http://en.wikipedia.org/wiki/Litmus

http://www.chemguide.co.uk/physical/acidbaseeqia/indicators.html

http://www.normalbreathing.com/CO2-blood-pH-respiratory-alkalosis.php

http://www.botany.org/bsa/careers/car-what.html