The function of an indicator in a titration process is to determine the equivalence point when two solutions have reached neutralization. An indicator can either be internal or external. An internal indicator is mixed in with the reactants and typically provides a visual prompt, while an external indicator is an electrochemical apparatus.
In chemistry, titration is an analytical technique used to ascertain the concentration of an unknown solution. This method involves a standard solution of known concentration called a titrant and another solution of unknown concentration called an analyte.
The titrant is carefully added to the analyte by means of a buret, until a state of equilibrium between the two solutions is obtained. The equivalence point, which refers to the instance when the analyte is entirely used up, is determined by using acid-base compounds, otherwise known as pH indicators, or external devices such as pH meters.
Weak acids and weak bases are typically used as pH indicators. These compounds are added to the titrant and analyte during the titration process. Common examples of pH indicators are methyl orange, methyl red, phenol red and phenolphthalein.
An observable color change indicates that the reaction is nearly or completely neutralized. However, pH indicators are not 100 percent accurate. In terms of precision, pH meters are the preferred indicators when titrating two solutions.