Filtering Funnels
Filtering funnels, also known as Buchner and Hirsch funnels, include a cylinder separated from the funnel with a fritted glass disc or perforated plate. Fritted glass disc funnels are immediately ready for use, while perforated plates call for filter paper moistened with liquid to prevent initial leakage.
Vacuum suction then draws the liquid through the filter and into the cylinder. Porcelain filtering funnels are resistant to acids and alkalis, except for hydrofluoric acid, but should not be used in the filtration of extremely corrosive reagents, which can slowly corrode their protective enamel. The funnels are glazed both outside and inside, except the rim, and are autoclavable.
What Is a Buchner Funnel Used for?
Buchner funnels are used in the laboratory for vacuum-assisted liquid filtering. In organic chemistry, these funnels are used to collect recrystallized compounds because they help remove moisture from the final product.
How Does a Buchner Funnel Work?
Buchner funnels consist of an open straight-sided cylindrical chamber that narrows to a tube- or pipe-shaped opening. The tube-like extension can be placed through a stopper, which is then placed into the top of a filtration or Buchner flask. Plastic versions may have a bung hole located at the side of the chamber to which a vacuum may be attached. Buchner funnels are reusable.
What Types of Buchner Funnels Are There?
The bottom of the Buchner funnel chamber may be perforated or contain a separate fritted disc. Filter paper is used for Buchner funnels with perforated lower surfaces. Place the filter paper of the preferred porosity inside the chamber, pre-wet, add the liquid, and apply the vacuum.
Filtration with a Buchner funnel proceeds more quickly than letting the liquid flow simply using gravity. Most Buchner funnels are also rated for a maximum vacuum pressure.
Fisherbrand™ Vacuum Filter Holders, Borosilicate Glass Funnels
For use with Fisherbrand Vacuum Filter Holder
Fisherbrand™ Reusable Glass Long-Stem Funnels
Promote faster, more effective filtering
Fisherbrand™ Reusable Glass Short-Stem Funnels
High resistance to chemical attack, mechanical, and thermal shock
Fisherbrand™ Porcelain Hirsch-Type Funnels with Perforated Plates
Highly resistant to chemical attack
Fisherbrand™ Porcelain Buchner Funnels with Fixed Perforated Plates
For suction filtration applications
DWK Life Sciences Kimble™ ValueWare™ 58° Addition Funnels
Fire polished long stems for long service life.
Corning™ PYREX™ Buchner Funnels with Fine Porosity Fritted Disc
Useful where filter paper would be attacked by material being filtered
DWK Life Sciences Kimble™ DISPOSAFLEX™ Polypropylene Luer Fitting only
These Polypropylene Luer Fittings are component parts for DISPOSAFLEX™ Columns.
Thermo Scientific™ Nalgene™ Reusable Bottle Top Filters
Combine the convenience of a bottle top filter with the savings of a reusable bottle top filter. Screw securely onto glass media bottles with 33 or 45mm neck sizes.
DWK Life Sciences Kimble™ KIMAX™ Buchner Kimflow™ Fritted Disc Funnels
Use where filtrate would attack paper filters and membranes
Thermo Scientific™ Nalgene™ Single Use Analytical Filter Funnels
Perform microbiological QC testing and analysis of water, food/beverage, raw material and finished product with these economical sterile disposable funnels.
Corning™ PYREX™ Hirsch-Type Funnel with Fine Porosity Fritted Disc
Ideal when necessary to wash precipitates and redissolve with chemicals that would attack filter paper
Sartorius Funnels for Combisart™
Reusable stainless steel Combisart™ Funnels for microbial enumeration and particle counting.
MilliporeSigma™ Glass Funnel for Vacuum Filtration
Designed to replace parts contained in glass vacuum filtration kits or provide for an alternative configuration