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Laboratory funnels are funnels that have been made for use in the chemical laboratory. There are many different kinds of funnels that have been adapted for these specialized applications. Filter funnels, thistle funnels (shaped like thistle flowers), and dropping funnels have stopcocks which allow the fluids to be added to a flask slowly. For solids, a powder funnel with a short and wide neck/stem is more appropriate as it prevents clogging.
When used with filter paper, filter funnels, Buchner and Hirsch funnels can be used to remove fine particles from a liquid in a process called filtration. For more demanding applications, the filter paper in the latter two may be replaced with a sintered glass frit.
Separatory funnels are used in liquid-liquid extractions.
Borosilicate glass is one of the most common materials of choice for laboratory applications due to its inertness compared with metals or plastics. However, plastic funnels made of non-reactive polyethylene are used for transferring aqueous solutions. Plastic is most often used for powder funnels which do not come into contact with solvents in normal use.
