These are tools used to quickly estimate the acidity or alkalinity of a solution. They consist of paper that has been treated with a natural dye extracted from lichens. When the treated paper comes into contact with a liquid, the dye changes color depending on the solution’s pH level, providing a visual indication of whether it is acidic, neutral, or alkaline. For instance, an acidic solution will typically cause the paper to turn red, while an alkaline solution will cause it to turn blue.
The ability to rapidly determine pH is valuable across numerous fields. In education, they offer a simple and safe way to demonstrate acid-base chemistry. In agriculture, they can help farmers assess soil pH levels, enabling them to make informed decisions about soil amendments. Their historical significance lies in their role as early indicators of acidity and alkalinity, predating more sophisticated electronic pH meters.
