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What is a Büchner Funnel?

What is a Büchner Funnel? Know the Setup, Structure, and Uses

A Büchner funnel is an efficient lab tool used to filter liquid from solid. It is employed in chemistry labs, scientific industries, and in schools and colleges.
Fatima Rangwala
Last Updated: Jul 16, 2017
Removing unwanted solid from liquid is the basic function of a Büchner funnel. The mixture of the liquid and solid is passed through the filter, which also has a piece of filter paper in the funnel, acting as a filtering agent. It blocks the solid particles, and the remains are passed into the collecting flask.
Setup and Structure
These funnels are made from a variety of materials like porcelain, plastic or glass. Though porcelain sets are used primarily, other sets made from plastic or glass are also used.
Setup: In a typical Büchner funnel, there is a Büchner flask made of glass which is placed on a flat table. On the top of the flask is another container with a modest hole in its bottom. This secondary container is placed on the top of the flask gently. The perforated hole faces downwards. In this elementary setup of the apparatus, the most important aspect is the piece of filter paper. It's placed in the funnel, so that the solids get segregated from the fluid. At the side hole there is another vacuum constituent which sucks out the air present in the flask.
Process: When a mixture is poured into the top container, due to the filter paper placed there, all the solid particles adhere to the filter paper, and the liquid freely flows through the filter paper into the flask placed below.
Following norms should be followed before using a Büchner funnel.
A: the filter paper should be moistened with a solvent prior to usage. This is to prevent the initial leakage. B: The pouring fluid which is to be filtered into another container is forced through a suction of vacuum. C: Also note that the solvent shouldn't exceed the necessary condition, else, the extra too would get sucked into the vacuum suction.
Uses of a Büchner Funnel
Vital in the field of organic chemistry, this funnel is chiefly used to collect the recrystallized compounds in the entire process. The vacuum suction dries the wet crystal compounds, such that the dry ones are left behind. Also, its use is often combined with sinter seals, a Büchner ring, and a flask. All these components are quite essential during the filtration process.
The other uses are:
  • In the make of: Glass Bottle
  • In liquefied gases for bench-top: Cryogenic Vacuum Flask
  • In the phase separation of plants and its constituents: Filtration Plants
  • In filter cloths: Industrial Filters
  • In economical, cool, long life, and tough pumps: Portable Vacuum Pumps
  • In distillation and extraction gas units: Sigma Process Plants
  • In steam jet ejector vacuum systems: Steam Jet Ejectors
This is perhaps one of the most essential and widely used piece of equipment you would find in any chemistry lab. It does help to speed up a chemical process and makes your work much easier. The funnel was named after an industrial chemist Ernst Büchner.