Centrifuge << SEHN truh fyooj >> is an instrument used to separate two liquids mixed together, or solid particles that are mixed in a liquid. The centrifuge causes the more dense substance to move to the bottom of the container, leaving the less dense substance on top. A centrifuge usually consists of a large wheel connected to an electric motor. The mixtures to be separated are balanced in containers on each side of the wheel. When the motor is turned on, the wheel rotates rapidly and the containers swing out from the center. A smaller centrifuge consists of a small rotating top in which test tubes of material can be placed at an angle. Centrifuges turn from 800 to 6,000 times per minute.
Centrifuges are commonly used in chemical and biological laboratories. They are used in medicine to prepare serums and plasma. Centrifuges separate the heavier blood cells or blood clot from the blood plasma or serum. They separate heavy bacteria from lighter kinds without destroying them. The cream separator is a centrifuge that takes cream out of whole milk, the cream being lighter than the skim milk that remains.
The ultracentrifuge is a newer kind of centrifuge with tremendous speed. It can spin at around 80,000 turns per minute. The rotating part of an ultracentrifuge touches nothing solid. It is balanced on a cushion of air. The ultracentrifuge whirls by means of jets of compressed air that touch the outer surface. Ultracentrifuges are used in the study of viruses.
See also Plasma.
