MODEL RELEASED. Titration experiment preparation by a student. He is using the pipette-filler (red) in his right hand to fill a volumetric pipette with acid from the beaker. The use of a volumetric pipette allows the transfer of a known volume of acid to the conical flask. The burette (down left) contains an alkali of known concentration, and is used to add a measured volume to neutralise the acid. An acid-base indicator (phenolphthalein, lower left) indicates the reaction's endpoint by a colourless (acidic) to pink (alkaline) colour change. The known concentrations and volumes allow the calculation of the concentration of the acid.