Editing Filtration (section)

===Methods===
Filters may be used for the purpose of removing unwanted liquid from a solid residue, cleaning unwanted solids from a liquid, or simply to separate the solid from the liquid.

There are many different methods of filtration; all aim to attain the [[Separation of mixtures|separation]] of substances. Separation is achieved by some form of interaction between the substance or objects to be removed and the filter. The substance that is to pass through the filter must be a [[fluid]], i.e. a [[liquid]] or [[gas]]. Methods of filtration vary depending on the location of the targeted material, i.e. whether it is dissolved in the fluid phase or suspended as a solid.
[[File: Hot Filtration set up.jpg|thumb|Hot filtration, solution contained in the Erlenmeyer flask is heated on a hot plate to prevent re-crystallization of solids in the flask itself]]
There are several laboratory filtration techniques depending on the desired outcome namely, hot, cold and [[Suction filtration|vacuum filtration]]. Some of the major purposes of obtaining the desired outcome are, for the removal of impurities from a mixture or, for the isolation of solids from a mixture.
[[File: Hot FIltration.jpg|thumb|left|Hot filtration for the separation of solids from a hot solution]]
'''Hot filtration''' method is mainly used to separate solids from a hot solution. This is done to prevent crystal formation in the filter funnel and other apparatus that come in contact with the solution. As a result, the apparatus and the solution used are heated to prevent the rapid decrease in temperature which in turn, would lead to the crystallisation of the solids in the funnel and hinder the filtration process.<ref>{{cite web|title=ORGANIC LABORATORY TECHNIQUES 3: Filtration Methods|url=http://www.chem.ucalgary.ca/courses/351/laboratory/filtration.pdf|publisher=[[University of Calgary]]|date=19 September 2013<!--from PDF source-->|archive-date=13 February 2015|archive-url=https://web.archive.org/web/20150213060129/http://www.chem.ucalgary.ca/courses/351/laboratory/filtration.pdf|url-status=live}}</ref>
One of the most important measures to prevent the formation of crystals in the funnel and to undergo effective hot filtration is the use stemless filter funnel. Due to the absence of a stem in the filter funnel, there is a decrease in the surface area of contact between the solution and the stem of the filter funnel, hence preventing re-crystallization of solid in the funnel, and adversely affecting the filtration process.

[[File: Cold Filtration.jpg|thumb|Cold filtration, the ice bath is used to cool down the temperature of the solution before undergoing the filtration process]]
'''Cold filtration''' method is the use of an ice bath to rapidly cool the solution to be crystallized rather than leaving it to cool slowly in the room atmosphere. This technique results in the formation of very small crystals as opposed to getting large crystals by cooling the solution at room temperature.

'''[[Suction filtration|Vacuum filtration]]''' technique is mostly preferred for small batches of solution to dry small crystals quickly. This method requires a [[Büchner funnel]], filter paper of a smaller diameter than the funnel, [[Büchner flask]], and rubber tubing to connect to a vacuum source.

'''Centrifugal filtration''' is carried out by rapidly rotating the substance to be filtered. The more dense material is separated from the less dense matter by the horizontal rotation.<ref name="Filtration">{{cite web |title=Filtration - Definition, Types, Functions & Quiz |url=https://biologydictionary.net/filtration/ |website=Biology Dictionary |date=3 March 2017}}</ref>

'''Gravity filtration''' is the process of pouring the mixture from a higher location to a lower one. It is frequently accomplished via simple filtration, which involves placing filter paper in a glass funnel with the liquid passing through by gravity while the insoluble solid particles are caught by the filter paper. Filter cones, fluted filters, or filtering pipets can all be employed, depending on the amount of the substance at hand.<ref name="Filtration"/> Gravity filtration is in widespread everyday use, for example for straining cooking water from food, or removing contaminants from a liquid.