Bucher funnels are commonly used in chemistry and industrial laboratories to remove solids from liquids. It consists of a glass funnel with a perforated or porous plate. Filter paper is placed over the perforated plate, and the liquid to be filtered is poured into the funnel. The liquid passes through the filter paper and is collected in a container below the funnel. Solid particles larger than the specified porosity of the filter paper will be retained on the surface of the paper.
Vacuum is often applied to the flask to speed filtration, so a good seal and a heavy walled flask are required.
There are two most common types of buchner funnels
- Buchner Funnel with perforated plate which uses filter paper
This style of buchner funnel uses filter paper. Filter paper can be easy to remove and exchange but allows a small amount of material around the sides. Quantitative filter paper can be purchased for accurate analysis of the filtered material.
- Buchner Funnel with fritted glass disc
The fritted disc is not removable which can be difficult to clean for certain solids such as carbon, but material will not pass around the sides and the fritted glass disc can withstand strong acids and bases.