Centrifuge

Another type of centrifuge is one in which the fluid to be separated is introduced into a container, and the container is then set into rapid rotational motion. Most beginning chemistry students are familiar with this instrument. It is commonly used as a substitute for filtration in the separation of a solid precipitate from the liquid in which it is suspended.

In this kind of machine, hollow tubes about 2 in (5 cm) in length are attached to arms radiating from the center of the machine. When the machine is turned on, the arms are spun around the center at a speed of about 30,000 revolutions per minute. The gravitational force experienced by materials inside the tubes-about 25,000 times that of gravity-causes the separation of materials much more efficiently than would a conventional filtration system.

Laboratory centrifuges have become invaluable tools in many kinds of scientific research. For example, today a widely used method of studying cells is to break apart a tissue sample and then centrifuge the resulting fluid. In this way, the discrete components of the cell can be separated and identified.