When carrying out volumetric analysis, it is essential to be able accurately to measure out volumes of liquids.
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For most purposes in the laboratory, it is quite sufficient to simply use a measuring cylinder/jug but when doing accurate volumetric work a higher level of precision is required.
In these cases a burette is used. A burette is a long cylinder with a tap at the bottom that allows accurate control of the liquid flowing out and can allow the volume to be read usually to the nearest 0.1 cm3.
While they do have other uses, burettes are most comonly encountered in titrations.