pH paper, also known as litmus paper or pH test strips, is a simple and cost-effective tool used to measure the acidity or alkalinity (pH) of a solution. It consists of small strips of paper that are impregnated with a mixture of dyes or chemicals that change color in response to changes in pH. The color change is then compared to a color chart or scale to determine the pH of the solution.

pH paper is widely used in various fields, including chemistry, biology, environmental science, and medicine. It is an essential tool in laboratories for conducting pH tests on chemical solutions. In the medical field, pH paper is used to test the pH of bodily fluids such as urine and saliva, which can provide valuable diagnostic information. pH paper is also used in aquariums and swimming pools to monitor and maintain the pH levels of the water, ensuring the health of aquatic organisms and the effectiveness of water treatment chemicals. Its simplicity and ease of use make pH paper a versatile and valuable tool for both professionals and hobbyists.