Funnel, Buchner

This Büchner funnel (often written Buchner funnel) is made of glazed porcelain, with straight sides and a fixed perforated plate. It's used for vacuum filtration, which separates a solid from a liquid far faster than letting it drain through a filter under gravity.

Filter paper isn't included. Use a paper that's big enough to cover all the holes, and wet it with a little of the liquid before you start so it seals and doesn't leak at first. The funnel sits in a Büchner flask, usually with a tapered rubber filter adapter cone (CH0421) to seal the joint, and the vacuum pulls the liquid through.

In organic chemistry this is the standard way to collect crystals after recrystallisation and draw off as much of the solvent as possible. Keep an eye on the liquid level in the flask. If it fills too far, liquid gets pulled into the vacuum equipment. Glass and plastic funnels are also made, but porcelain is the traditional choice.

We stock sizes from 35mm to 300mm (35, 50, 60, 75, 80, 100, 105, 125, 150, 200, 210, 250 and 300mm). The table shows the filter paper size and volume for most of them, and our guide What size filter paper do I need for my funnel? goes into more detail.

To complete the setup you'll need a Buchner filtering flask and rubber filter cones.