Centrifuge by Laval

Topics: Earth, Centrifuge, Rotation Pages: 2 (404 words) Published: September 16, 2008
Developed by Gustaf de Laval

Centrifuge is a device in which solid or liquid particles of different densities are separated by rotating them in a tube in a horizontal circle. The dense particles tend to move along the length of the tube to a greater radius of rotation, displacing the lighter particles to the other end. English military engineer Benjamin Robins (1707-1751) invented a whirling arm apparatus to determine drag. In 1864, Antonin Prandl invented the first dairy centrifuge in order to separate cream from milk. And in 1879, Gustaf de Laval demonstrated the first continuous centrifugal separator, making its commercial application feasible. Using high pressure steam in a turbine that had oil-fed bearings meant that some of the steam contaminated the lube-oil, and as a result, perfecting commercial steam-turbines required that he also develop an effective oil/water separator. After trying several methods, he concluded that a centrifugal separator was the most affordable and effective method. He developed several types, and their success established the centrifugal separator as a useful device in a variety of applications. Protocols for centrifugation typically specify the amount of acceleration to be applied to the sample, rather than specifying a rotational speed such as revolutions per minute. The acceleration is often quoted in multiples of g, the standard acceleration due to gravity at the Earth's surface. This distinction is important because two rotors with different diameters running at the same rotational speed will subject samples to different accelerations. A laboratory centrifuge is a piece of laboratory equipment, driven by a motor, which spins liquid samples at high speed. There are two main sizes for laboratory centrifuges. The larger ones are known simply as centrifuges; samples are contained in centrifuge tubes or centrifuge tips. The smaller centrifuges are known as microcentrifuges or microfuges, and microcentrifuge...
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