Litmus comes from the Norse word meaning "to dye, or color." The lichens that are on litmus paper have been used to dye cloth for hundreds of years. Lichens are a scientific oddity in that they are a combination of a fungi and an alga living as one. It is believed that a French chemist developed litmus paper during the early 1800s.
The paper is the most recognized in its field for determining pH levels. One of its most common uses is the classroom. Science teachers across the globe use the paper when teaching chemistry. Because of its popularity, the paper has made its way into pop culture. The term "litmus test" is commonly used to refer to a situation in which a single factor determines the outcome.
Knowing pH is important in the field of biology. Most life forms have a very small range of pH levels that they can survive in. With human beings, for example, the slightest shift in pH levels in a human's blood can result in serious bodily damage and death. Litmus paper is used to test certain environmental and biological factors. For pregnant women, a pH test is done to test urine acidity.
A real-world example of the importance of pH testing can be found when looking at plant life. Soil that is too acidic will not foster the growth and development of plant life. Therefore, a basic fertilizer, composed of calcium carbonate, is mixed into the soil to allow the plants to grow.
Litmus paper, can indicate whether a substance is basic, acidic or neutral, but it cannot give a numerical value to the grouping. It cannot indicate how acidic or basic a substance is. A pH meter is used to acquire this information.