Buret
Definition and meaning of Buret in chemistry.
A buret is a long, graduated glass tube fitted with a stopcock at the bottom, used to deliver precise, variable volumes of a liquid, most commonly the titrant in a titration.
In more detail
The stopcock lets the analyst release liquid drop by drop while a column of graduated markings shows exactly how much has been dispensed. Volume delivered is found by subtracting the initial reading from the final reading, so the buret does not need to be filled to any exact starting mark. Readings are taken at eye level and estimated to the nearest 0.01 mL, using the bottom of the meniscus for most solutions (the top for opaque or strongly colored ones). Because it measures dispensed volume with high precision, the buret is essential for determining unknown concentrations in acid-base, redox, and complexometric titrations.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Typical capacity | 50 mL (also common: 10 mL, 25 mL) |
| Readability | Marked in 0.1 mL increments, read to nearest 0.01 mL |
| Primary use | Delivering titrant in volumetric titrations |
In an acid-base titration, a 50 mL buret is filled with 0.100 M NaOH and used to titrate 25.00 mL of HCl solution containing a phenolphthalein indicator; the volume of NaOH added when the solution turns faint pink (the endpoint) is read from the buret and used to calculate the HCl concentration.
Frequently asked questions
How do you read a buret correctly?
Position your eye level with the liquid surface, read the bottom of the meniscus (top for dark/opaque liquids), and record both an initial and final reading; the volume delivered is the difference between the two.
How is a buret different from a pipette?
A buret dispenses a variable, adjustable volume through a stopcock and is read before and after use, while a pipette is designed to deliver one specific, fixed volume in a single transfer.