The approximate pH of a solution can be determined by placing a drop of the solution on a piece of indicator paper. Two types of pH paper are commonly used: litmus paper and universal (Alkacid) paper. The type of pH paper used is dependent on the type of measurement and degree of accuracy required.
IMAGE. Red and blue litmus paper. Top: Red litmus paper with a drop of base placed on it (where the red paper has turned blue). Bottom: Blue litmus paper with a drop of acid placed on it (where the blue paper has turned red).
IMAGE. Universal paper is capable of indicating a range of pH values.
