Burette
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A burette (also buret) is a vertical cylindrical piece of laboratory glassware with a volumetric graduation on its full length and a precision tap, or stopcock, on the bottom. It is used to dispense known amounts of a liquid reagent in experiments for which such precision is necessary, such as a titration experiment. Burettes are extremely precise: class A burettes are accurate to ±0.05 mL.
Using a Burette
The precision of a burette makes careful measurement with a burette very important to avoid systematic error. When reading a burette, the viewer's eyes must be at the level of the graduation to avoid parallax error. Even the thickness of the lines printed on the burette matters; the meniscus of the liquid should be touching the top of the line you wish to measure from. A common rule of thumb is to add 0.02 mL if the bottom of the meniscus is touching the bottom of the line. Due to the precision of the burette, even a single drop of liquid hanging from the bottom of a burette should be transferred to the receiving flask, usually by touching the drop to the side of the receiving flask and washing into the solution with the experimental solvent (usually water). Through careful control of the stopcock and rinsing, even partial drops of liquid can be added to the receiving flask.
External links
- Using a Burette (http://www.dartmouth.edu/~chemlab/techniques/buret.html) from ChemLab at Dartmouth College
- Image of a burette (http://core.ecu.edu/chem/chemlab/equipment/images/burette.jpg)
