Centrifuge
From Freepedia
Image:Centrifugetesttube small.jpg Image:Tabletop centrifuge.jpg A centrifuge is a piece of equipment that puts a substance in circular motion in order for the centrifugal force to separate a fluid from a fluid or from a solid substance. Generally, a motor drives the rotary motion of the sample. There are many different kinds of centrifuges, often for very specialised purposes.
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History and predecessors
English military engineer Benjamin Robins (1707-1751) invented a whirling arm apparatus to determine drag.
The ultracentrifuge is a device invented in 1925 by Theodor Svedberg, which by use of very high acceleration, and allowing the observation of sedimentation rates for macromolecules, allowed for the determination of their approximate molecular weights. Svedberg won the 1926 Nobel Prize in Chemistry for his invention.
Different types and uses
- Simple centrifuges are used in biology and biochemistry for isolating and separating biocompounds on the basis of molecular weight. These will tend to rotate at a slower rate than an ultracentrifuge, and have larger rotors, and be optimized for holding large quantities of material at intermediate acceleration.
- Standalone centrifuges for drying (hand-washed) clothes - usually with a water outlet.
- Other centrifuges, the first being the Zippe-type, are used to separate isotopes, and these kinds of centrifuges are in use in nuclear power and nuclear weapon programs.
- Exceptionally large centrifuges are used to test the reactions of pilots and astronauts to acceleration above those experienced in the Earth's gravity.
- In soil mechanics, centrifuges utilize centrifugal acceleration to match soil stresses in a scale model to those found in reality.
- Large industrial centrifuges are commonly used in water and wastewater treatment to dry sludges. The resulting dry product is often termed cake and the water leaving a centrifugal after most of the solids have been removed is called centrate.
- Centrifuges are used in the attraction Mission: SPACE, located at the EPCOT Center in Walt Disney World. Florida, which propels riders using a combination of a centrifuge and a motion simulator to simulate the feeling of going into space.
Use and safety
Because of the kinetic energy stored in the rotor head, those who have experienced an ultracentrifuge's losing a rotor compare the experience to having a bomb explode nearby.
Also, many laboratory centrifuges require a counterweight to be placed opposite the test tube or whatever being spun. Not doing so may seriously damage the centrifuge and create an unpleasant sound as the rotor and shaft scrape the casing.
See also
