Editing Centrifugation (section)

{{Short description|Mechanical process}}
{{Use dmy dates|date=November 2017}}

[[File:Centrifuga_Hermle_2.jpg|thumb|[[Laboratory centrifuge]]]]
'''Centrifugation''' is a mechanical process which involves the use of the [[centrifugal force]] to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed.<ref name="Fischer"/> The denser components of the mixture migrate away from the axis of the [[centrifuge]], while the less dense components of the mixture migrate towards the axis. Chemists and biologists may increase the effective [[gravitational force]] of the test tube so that the [[precipitate]] (pellet) will travel quickly and fully to the bottom of the tube. The remaining liquid that lies above the precipitate is called a [[supernatant]] or supernate.

There is a correlation between the size and [[density]] of a particle and the rate that the particle separates from a heterogeneous mixture, when the only force applied is that of gravity. The larger the size and the larger the density of the particles, the faster they separate from the mixture. By applying a larger effective gravitational force to the mixture, like a centrifuge does, the separation of the particles is accelerated. This is ideal in industrial and lab settings because particles that would naturally separate over a long period of time can be separated in much less time.<ref>{{cite web|last1=Frei|first1=Mark|title=Centrifugation Basics|url=http://www.sigmaaldrich.com/technical-documents/articles/biofiles/centrifugation-basics.html|website=Sigma-Aldrich|access-date=10 May 2016}}</ref>

The rate of centrifugation is specified by the [[angular velocity]] usually expressed as [[revolutions per minute]] (RPM), or acceleration expressed as [[g-force|''g'']]. The conversion factor between RPM and ''g'' depends on the [[radius]] of the centrifuge [[wikt:rotor|rotor]]. The particles' [[settling]] velocity in centrifugation is a function of their size and shape, centrifugal acceleration, the volume fraction of solids present, the [[density]] difference between the particle and the liquid, and the [[viscosity]]. The most common application is the separation of solid from highly concentrated suspensions, which is used in the treatment of sewage sludges for dewatering where less consistent sediment is produced.<ref>{{Cite web |title=Centrifugation|publisher=Lenntech |access-date= 15 October 2013|url=https://www.lenntech.com/library/clarification/clarification/centrifugation.htm}}</ref>

The centrifugation method has a wide variety of industrial and laboratorial applications; not only is this process used to separate two miscible substances, but also to analyze the [[hydrodynamic]] properties of macromolecules.<ref>{{cite book|last1=Garrett|first1=Reginald H.|last2=Grisham|first2=Charles M.|title=Biochemistry|date=2013|publisher=Brooks/Cole, Cengage Learning|location=Belmont, CA|isbn=9781133106296|pages=111|edition=5th}}</ref> It is one of the most important and commonly used research methods in [[biochemistry]], [[cell biology|cell]] and [[molecular biology]]. In the chemical and food industries, special centrifuges can [[continuous process|process a continuous stream]] of particle turning into separated liquid like plasma. Centrifugation is also the most common method used for [[uranium enrichment]], relying on the slight mass difference between atoms of [[Uranium-238|U-238]] and [[U-235]] in [[uranium hexafluoride]] gas.<ref>{{Cite web |last = Zielinski |first = Sarah |title = What Is Enriched Uranium? |work = Smithsonian Magazine |access-date = 2020-11-22 |url = https://www.smithsonianmag.com/science-nature/what-is-enriched-uranium-17091828/}}</ref>