A device designed to visually signal the presence or concentration of a specific substance, or to reflect the acidity or alkalinity of a solution, comprises a small piece of material impregnated with one or more chemical compounds. These compounds undergo a noticeable change, typically a color shift, upon exposure to the target substance or a particular pH level. This change allows for a rapid, qualitative or semi-quantitative assessment. An example includes those used to test the pH of water, where the strip changes color to indicate whether the water is acidic, neutral, or alkaline.
These tools offer a convenient and often inexpensive means of analysis across various applications. Their portability and ease of use make them invaluable in fields ranging from environmental monitoring and food safety to clinical diagnostics and educational settings. Historically, the development of these indicators stems from the need for simple methods to assess chemical properties without requiring complex laboratory equipment.
