Filter Flask (Buchner flask) also known as a vacuum flask, Filter Flask, suction flask, side-arm flask or Bunsen flask, is a thick-walled Erlenmeyer flask with a short glass tube and hose barb protruding about an inch from its neck.
- Fitted with glass vacuum side arm connection
- Made from heavy wall Borosilicate 3.3 glass to withstand high vacuum
- Each flask is fitted with a removable “gucko” gasket
A Buchner Flask is a laboratory glassware that is used for receiving a filtering liquid and that is usually of heavy-walled glass and is often provided with a side tube to connect with a suction pump.
Buchner Flask short tube and hose barb effectively act as an adapter over which the end of a thick-walled flexible hose (tubing) can be fitted to form a connection to the flask. The other end of the hose can be connected to source of vacuum such as an aspirator, vacuum pump, or house vacuum. Preferably this is done through a trap (see below), which is designed to prevent the sucking back of water from the aspirator into the filter flask.
The thick wall of the filter flask provides it the strength to withstand the pressure difference while holding a vacuum inside. It is primarily used together with a Büchner funnel fitted through a drilled rubber bung or an elastomer adapter at the neck on top of the flask for the filtration of samples. The Büchner funnel holds the sample isolated from the suction by a layer of filter paper. During filtration, the filtrate enters and is held by the flask while the residue remains on the filter paper in the funnel.
The filter flask can also be used as a vacuum trap in a vacuum line to ensure that no fluids are carried over from the aspirator or vacuum pump to the evacuated apparatus or vice versa.
- Buchner filtration has great advantage in filtration in a sense that it proceeds much more quickly than simply allowing the liquid to drain through the filter medium via the force of gravity.
- Filtering flask is used for vacuum filtration or distillation. The graduations are approximate and not intended for accurate liquid measurement.