Centrifuge
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A centrifuge is a piece of laboratory equipment that applies centrifugal force to a sample. 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.
- Washing machines use a centrifuge to partially remove the water from wet clothes.
- 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 utilise centrifugal acceleration to match soil stresses in a scale model to those found in reality.
Use and safety
Because of the kinetic energy stored in the rotor head, those who have experienced an ultracentrifuge 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.