Burette

Malay: Buret · Chinese: 滴定管

A burette is a long graduated glass tube fitted with a tap (stopcock) at the bottom. It delivers a variable volume that you read from its scale, which lets you add liquid a little at a time and know exactly how much has run out. Its main use is in titration, where acid or alkali is added drop by drop until the reaction is just complete. Because the SPM Chemistry papers (4541) include titration as a core practical, you must know how a burette is read and used.

To use it, you fill the burette, take the initial reading, then open the tap to add liquid until the end point, and take the final reading. The volume delivered is the final reading minus the initial reading, for example 24.60 cm³ minus 0.00 cm³. Both readings are taken from the bottom of the meniscus at eye level to avoid parallax error, and the scale usually reads to the nearest 0.05 cm³.

The confusion to avoid is between a burette and a pipette. A pipette delivers one fixed volume, while a burette delivers whatever variable volume you choose to run out and read. Mixing them up leads to choosing the wrong apparatus in a titration question, which costs marks. Note too that a burette reads from top to bottom, so the numbers increase down the tube, and forgetting this is an easy way to record the volume the wrong way round.

Within this chapter the burette pairs with the pipette as the two accurate-volume instruments of titration. Our teachers walk you through a full burette reading so you record volumes to the correct precision.