Büchner funnel
Encyclopedia
A Büchner funnel is a piece of laboratory
equipment used in suction filtration
. It is traditionally made of porcelain
, but glass
and plastic
funnels are also available. On top of the funnel-shaped part there is a cylinder with a perforated plate separating it from the funnel. The Hirsch funnel has a similar design; it is used similarly, but for smaller quantities of material. The main difference is that the plate is much smaller, while the walls of the funnel angle outward instead of being vertical.
The filtration material, usually filter paper
, is placed on the plate, and the filter paper is moistened with a solvent to prevent initial leakage. The liquid
to be filtered is poured into the cylinder and drawn through the perforated plate by vacuum
suction.
The main advantage in using this type of filtration is that it proceeds much more quickly (several orders of magnitude) than simply allowing the solvent to drain through the filter medium via the force of gravity. It is essential that the amount of solvent being used be limited to less than what would overflow the flask, otherwise the solvent will be drawn into the vacuum equipment. If the vacuum is provided by a water flow device, an overflow of the solvent could result in the spilling of a hazardous solvent into the wastewater stream, a potential violation of the law, depending on the solvent. The potential for overflow and the potential for water to be drawn back into the flask can be reduced by using a trap between the flask and the vacuum source.
It is used in organic chemistry labs to assist in collecting recrystallized compounds. The suction allows the wet recrystallized compound to dry out such that the pure dried crystal compound is left remaining. However, it is often the case that further drying is required, by an oven or other means, in order to remove as much residual solvent as possible.
It is often used in combination with a Büchner flask
, Büchner ring and sinter seals. A vacuum tight seal and stability of the Büchner flask and filter are essential during the filtration process. A Büchner ring can be used with Büchner funnels, flasks, glass crucibles and gooch crucibles. The wide flange and large surface contact ensures an excellent vacuum tight seal whilst the rings are easy to remove and offer excellent support to even the largest funnels.
It is commonly thought to be named for the Nobel Laureate, Eduard Buchner
(without umlaut), but it is actually named for the industrial chemist Ernst Büchner
.
Laboratory
A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...
equipment used in suction filtration
Suction filtration
Suction filtration is a chemistry laboratory technique which allows for a greater rate of distillation. Whereas in normal filtration gravity provides the force which draws the liquid through the filter paper, in suction filtration a pressure gradient performs this function...
. It is traditionally made of porcelain
Porcelain
Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...
, but glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
and plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
funnels are also available. On top of the funnel-shaped part there is a cylinder with a perforated plate separating it from the funnel. The Hirsch funnel has a similar design; it is used similarly, but for smaller quantities of material. The main difference is that the plate is much smaller, while the walls of the funnel angle outward instead of being vertical.
Filter paper
Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solids from liquids or air.-Properties:Filter paper comes in various porosities and grades depending on the applications it is meant for...
, is placed on the plate, and the filter paper is moistened with a solvent to prevent initial leakage. The liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
to be filtered is poured into the cylinder and drawn through the perforated plate by vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
suction.
The main advantage in using this type of filtration is that it proceeds much more quickly (several orders of magnitude) than simply allowing the solvent to drain through the filter medium via the force of gravity. It is essential that the amount of solvent being used be limited to less than what would overflow the flask, otherwise the solvent will be drawn into the vacuum equipment. If the vacuum is provided by a water flow device, an overflow of the solvent could result in the spilling of a hazardous solvent into the wastewater stream, a potential violation of the law, depending on the solvent. The potential for overflow and the potential for water to be drawn back into the flask can be reduced by using a trap between the flask and the vacuum source.
It is used in organic chemistry labs to assist in collecting recrystallized compounds. The suction allows the wet recrystallized compound to dry out such that the pure dried crystal compound is left remaining. However, it is often the case that further drying is required, by an oven or other means, in order to remove as much residual solvent as possible.
It is often used in combination with a Büchner flask
Büchner flask
A Büchner flask, also known as a vacuum flask, filter flask, side-arm flask or Kitasato flask, is a thick-walled Erlenmeyer flask with a short glass tube and hose barb protruding about an inch from its neck. The short tube and hose barb effectively acts as an adapter over which the end of a...
, Büchner ring and sinter seals. A vacuum tight seal and stability of the Büchner flask and filter are essential during the filtration process. A Büchner ring can be used with Büchner funnels, flasks, glass crucibles and gooch crucibles. The wide flange and large surface contact ensures an excellent vacuum tight seal whilst the rings are easy to remove and offer excellent support to even the largest funnels.
It is commonly thought to be named for the Nobel Laureate, Eduard Buchner
Eduard Buchner
Eduard Buchner was a German chemist and zymologist, awarded with the 1907 Nobel Prize in Chemistry thanks to his work on fermentation.-Early years:...
(without umlaut), but it is actually named for the industrial chemist Ernst Büchner
Ernst Büchner
Ernst Wilhelm Büchner was an industrial chemist and the inventor of the Büchner funnel and Büchner flask. Ernst was the nephew of the playwright Georg Büchner.-External links:...
.
Further reading
- The Agitated Nutsche FilterAgitated Nutsche FilterAgitated Nutsche filter is a filtration technique used in applications such as dye, paint, and pharmaceutical production and waste water treatment...
is the industrial-scale analog of the Büchner funnel.