Buchner Funnel

Diagram:

(Diagram and components of a Buchner Funnel)

Additional highlights:

• Cylindrical wall – to prevent over-filling
• Fritted bottom – for even, smooth filtering
• Useful for collecting precipitated crystals from a solution

Construction:

Each Buchner Funnel is a solid, cylindrical construction with a large, fritted (or perforated) top opening consisting of many tiny holes. The porcelain chamber narrows to a tube-shaped hole on the bottom, through which liquids can pass.

The narrow bottom portion of the funnel can be placed through a rubber stopper to create an air-tight seal, forcing both liquids and gases to pass through the numerous tiny holes at the top.

The liquid drains into a Buchner Flask (or filter flask). The receiving flask has a vacuum attachment, to which vacuum tubing can be connected.

By placing qualitative filter paper on top of the perforations, you can effectively filter substances by means of vacuum filtration.

The key benefit of using this style of filtration is that the liquid moves through the funnel much faster than with the force of gravity alone (several orders of magnitude, in fact).

Porcelain or plastic Buchner Funnels?

The Buchner Funnels we sell are made from premium porcelain, which is the preferred option over plastic or glass.

We recommend porcelain for vacuum filtration, because it’s easier to clean and offers greater chemical resistance. It can also handle more extreme temperatures than plastic. Porcelain is the industry standard for vacuum filtration.

Designed to be reusable.

If properly cared for, Buchner Funnels can last you many years in your lab. Make sure to clean them thoroughly in between uses and that the pores do not become clogged over time, reducing the effectiveness of the filtration.

Great for collecting recrystallized compounds.

In organic chemistry and vacuum filtration (some of the most common applications for this product category), laboratories make use of these funnels to help collect recrystallized compounds.

You may need additional drying, for example, through the use of a vacuum oven. This can help you remove even more of the remaining liquid from the compound you are attempting to filter.

Create an air-tight seal.

Before use, insert the Buchner Funnel through a rubber cork (with a hole drilled through the center). This holds the funnel in place and creates an air-tight seal.

Filter paper must be placed over the holes of the funnel to prevent clogging and/or leakage.

Before use, moisten the filter paper inside the funnel to lightly adhere the paper to the funnel, helping “stick” the filter paper to the top of the funnel. This reduces the chance of particles coming between the filter paper and the funnel itself.

Important note about safety:

Always make sure that you don’t overfill the chamber of the funnel. If spillage occurs, it can leak into your vacuum pump, causing a number of unwanted outcomes.

*Notes: 

• All measurements are in O.D.
• Make sure to buy a rubber cork and the right sized filter paper for use with these funnels, as both of these things will be needed to operate your funnel properly.
• Rubber corks can also be drilled out to fit bigger stems, just as bigger filter paper may also be cut down for use in smaller funnels. You can also enhance your filter flask with our black rubber filter aid!