A Büchner funnel is a piece of

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as schools ...

equipment used in

filtration Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filte ...

. It is traditionally made of

porcelain Porcelain (), also called china, is a ceramic material made by heating Industrial mineral, raw materials, generally including kaolinite, in a kiln to temperatures between . The greater strength and translucence of porcelain, relative to oth ...

, but

glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...

and

plastic Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...

funnels are also available. On top of the funnel-shaped part there is a cylinder with a fritted glass disc/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 of a Hirsch funnel is much smaller, and the walls of the funnel angle outward instead of being vertical. A

funnel A funnel is a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening. Funnels are usually made of stainless steel, aluminium, glass, or plastic. The material used in its constructi ...

with a fritted glass disc can be used immediately. For a funnel with a perforated plate, filtration material in the form of

filter paper Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solid particles from liquids or gases. The raw materials are typically different pulp (paper), paper pulps. The pulp may be ...

is placed on the plate, and the filter paper is moistened with a liquid to prevent initial leakage. The

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

to be filtered is poured into the cylinder and drawn through the perforated plate/fritted glass disc by

vacuum A vacuum (: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective (neuter ) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressur ...

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 liquid to drain through the filter medium via the force of gravity. It is essential that the amount of liquid being used is limited to less than what would overflow the flask; otherwise, the liquid will be drawn into the vacuum equipment. If the vacuum is provided by a water flow device, an overflow of the liquid could result in the spilling of a hazardous liquid into the wastewater stream, a potential violation of the law, depending on the liquid. 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 liquid 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 after the Nobel Laureate

Eduard Buchner Eduard Buchner (; 20 May 1860 – 13 August 1917) was a German chemist and Zymurgy, zymologist, awarded the 1907 Nobel Prize in Chemistry for his work on fermentation (biochemistry), fermentation. Biography Early years Buchner was born in Mun ...

(without umlaut), but it is actually named after the industrial chemist Ernst Büchner.Büchner, Ernst (1888
"Filtration vermittelst des Dr. R. Hirsch'schen Patent Trichters"
(Filtration by means of Dr. R. Hirsch's patented funnel), ''Chemiker-Zeitung'', 12 (78) : 1277.

See also

References

Further reading