End point

First do a rough trial to locate the approximate end point. Then repeat: add acid more slowly as you approach that volume, and drop by drop near the end, stopping when the indicator's colour change persists. A sharp-change indicator such as phenolphthalein or methyl orange makes the end point easier to judge than universal indicator's gradual range of colours.

The indicator’s colour change marks the end point; record the volume delivered from the burette. This establishes the proportions for those solutions. It does not mean that equal volumes must be mixed: the required volumes depend on the solutions and the reaction.

A few drops of a suitable indicator are therefore added. Its colour change marks the end-point. The aim is to identify the first permanent colour change without adding an unnecessary excess of solution.

An indicator shows when the reaction has just reached its end point. Careful volume measurements matter because the result can be used to determine the concentration of an unknown acid or alkali.