A titration finds exactly how much acid reacts with a given volume of alkali. Use a pipette to measure 25.0 cm3 of alkali into a conical flask and add a few drops of a suitable indicator, such as methyl orange or phenolphthalein. Fill a burette with the acid and record the starting reading.
Add the acid to the flask a little at a time, swirling all the time. Near the end point, add it drop by drop. The end point is when the indicator just changes colour, for example phenolphthalein goes from pink to colourless. Record the final reading. The volume of acid added is the titre. For example, a burette that reads 0.50 cm3 at the start and 21.30 cm3 at the end gives a titre of 20.80 cm3. Repeat until the results are concordant, meaning very close together.
To get a pure salt, repeat with the same volumes of alkali and acid but with no indicator, so the salt is not contaminated. The solution contains only salt and water. Heat it to evaporate some of the water, leave it to crystallise, then filter and dry the crystals.
