The acidity of a solution is typically assessed experimentally by measurement of its pH. The pOH of a solution is not usually measured, as it is easily calculated from an experimentally determined pH value. The pH of a solution can be directly measured using a pH meter ([link]).
The pH of a solution may also be visually estimated using colored indicators such as the solution indicator and pH strips shown below. The acid-base equilibria that enable use of these indicator dyes for pH measurements are described in a later section of this chapter.