Ph test paper for measuring PH value First, put the PH test paper on a white porcelain plate or a glass plate, then dip a small amount of liquid in the test paper with a glass tie, and compare the color displayed by the PH test paper with the standard colorimetric card, thus measuring the PH value of the solution.
Litmus test solution and phenolphthalein test solution are used to measure pH value. Litmus test solution turns red in acid and blue in alkali. Phenolphthalein does not change color in acid, but turns red in alkali.