PH litmus test paper is a simple and widely used tool for determining the acidity or alkalinity of a solution. Made from paper infused with natural dyes derived from lichens, it changes color upon contact with a liquid, providing a quick visual indication of the pH level.

The paper typically turns red in acidic solutions (pH < 7), blue in alkaline solutions (pH > 7), and may remain purple or show no significant change in neutral conditions (pH ≈ 7). While it does not provide a precise numerical pH value, it is effective for basic classification as acidic, neutral, or alkaline.

Its advantages include ease of use, portability, low cost, and rapid results. However, it is less accurate than electronic pH meters and may be affected by highly colored or turbid samples.

Commonly applied in educational settings, home experiments, and preliminary testing in laboratories, litmus paper remains a fundamental tool for initial pH assessment across various fields.