Büchner funnel

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Büchner funnel is a piece of laboratory equipment used in suction filtration. It is traditionally made of porcelain, but glass and plastic funnels are also available. On top of the funnel-shaped part there is a cylinder with a perforated plate separating it from the funnel. The Hirsch funnel has a similar design; it is used similarly, but for smaller quantities of material. The main difference is that the plate is much smaller, while the walls of the funnel angle outward instead of being vertical.

The filtration material, usually filter paper, is placed on the plate, and the filter paper is moistened with a solvent to prevent initial leakage. The liquid to be filtered is poured into the cylinder and drawn through the perforated plate by vacuum suction.

It is usually used in organic chemistry labs to assist in purifying recrystallized compounds. The suction allows the wet recrystallized compound to dry out such that the pure dried crystal compound is left remaining. Although, it is often the case that further drying is required, by an oven or other means, in order to remove as much residual solvent as possible.

It is often used in combination with a Büchner flask.

It is commonly thought to be named for the Nobel Laureate, Eduard Buchner, but it is actually named for the industrial chemist Ernst Büchner.

[edit] References

• Jensen, William B. (September 2006). "The Origins of the Hirsch and Büchner Vacuum Filtration Funnels" (PDF). Journal of Chemical Education 83 (9): 1283.