Handling of glass burettes
What are burettes?
Burettes are precise volumetric instruments used to carry out exact analyses. Conventional burettes consist of a long, graduated glass tube and feature a device to deliver a solution precisley, typically a stopcock or valve. They are calibrated to “Ex” (TD = to deliver).
Burettes are primarily used for titrations in volumetric analysis. The scale indicates the volume of liquid delivered until the required reaction point or endpoint is reached.
- Calibration
Class AS: 'Ex + 30 s'
Class B: 'Ex'
What types of burettes exist?
Burettes are available in various designs that differ in terms of construction, operation, and readability:
Glass burettes
Glass burettes are available with different stopcock and valve designs. There are also Schellbach burettes featuring a colored stripe that makes it easier to read the meniscus.
Automatic burettes / titration apparatus
Automatic burettes and titration apparatus feature automatic zero-point adjustment at the top, allowing convenient filling from a reservoir bottle.
There are also digital burettes, in which the delivered volume is measured electronically and shown on a display, such as the Titrette® from BRAND. However, this article focuses on conventional glass burettes and their different designs.
How to work with glass burettes
1. Rinse the burette with the standard solution to be used, and align burette tube vertically.
2. Fill the burette slightly above the zero mark. To prime the stopcock, drain the burette no further than the nominal capacity.
3. Refill the burette with titrant free of air bubbles to approx. 5 mm above the zero mark.
4. Drain liquid to set the zero point accurately. Important: Meniscus must be read at eye level (parallax-free level). Automatic burettes: Fill to approx. 5 mm above the zero mark. This is adjusted automatically after air release.
5. Wipe off any drops adhering to the discharge tip.
6. Open the stopcock and slowly add titrant to the sample (containing the indicator). The discharge tip must not touch the wall of the vessel. Keep swirling the sample vessel lightly while adding titrant, or place it on a magnetic stirrer.
7. Read the discharged volume at eye level.
8. Any drops remaining on the tip of the stopcock should be wiped against the vessel wall and rinsed down. It is part of the titrated volume.
Note on waiting time
Note on titration
