Vacuum filtration is used primarily to collect a desired solid, for instance, the collection of crystals in a recrystallization procedure. Vacuum filtration uses a Buchner funnel and a side-arm flask. Vacuum filtration is faster than gravity filtration, because the solvent or solution and air is forced through the filter paper by the application of reduced pressure.
Do not use vacuum filtration to filter a solid from a liquid if it is the liquid that you want, and if the liquid is low boiling. Any solvent which boils at about degrees or lower will boil off under the reduced pressure in the vacuum flask.
Filtration under vacuum using a Buchner funnel is used when you want to isolate the precipitate the solid for further work or analysis. All of this apparatus is available together in a basic vacuum filtration kit — this saves you finding parts that will fit together and is a good option for starting out in vacuum filtering. Gravity filtration is the method of choice to remove solid impurities from an organic liquid.
The impurity can be a drying agent or an undesired side product or leftover reactant. Gravity filtration can be used to collect solid product, although generally vacuum filtration is used for this purpose because it is faster.
Source: Camlab Limited. There are two types of filtration which are commonly used in the laboratory and it is important to select the correct type for the work you are doing. Vacuum Filtration — also known as Buchner filtration — for when you need to isolate the precipitate the solid. Filtration under vacuum using a Buchner funnel is used when you want to isolate the precipitate the solid for further work or analysis.
You may also use a spatula to agitate the precipitate on the filter paper for thorough drying, or to remove the precipitate after the filtration is finished. Gravity Filtration — also known as simple filtration — for when you need to isolate the filtrate the liquid. A basic filtration under gravity is used when you are removing the solid precipitate to isolate the filtrate, the liquid, for further work or testing.
These products include a variety of nebulizers, torches, spray chambers and other glassware. Vacuum filtration is often used to speed up the filtration process. Related questions How is separating components of mixtures different from compounds? What are different methods used to separate mixtures? How can foam properties be utilized to separate mixtures? How can compounds in a mixture be separated? How can mixtures be separated using physical properties?
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