Centrifuge

The basic centrifuge design described above can be adapted for use in many different settings. Industrial centrifuges, for example, tend to be quite large, ranging in size from 4 in to 4 ft (10 cm to 1.2 m) in diameter, with rotational velocities from 1,000 to 15,000 revolutions per minute. They can be designed so as to remove separated portions continuously, all at once after the machine has been stopped, or intermittently.

Large-scale centrifugation has found a great variety of commercial and industrial uses. For example, the separation of cream from milk has been accomplished by this process for well over a hundred years. Today, centrifuges are used to remove water from oil and from jet fuel and in the removal of solid materials from waste water during the process of water purification.

A centrifuge for use with very small particles of similar weight—the ultracentrifuge—was first developed by the Swedish chemist Theodor Svedberg in about 1923. In the ultracentrifuge, containers no more than about 0.2 in (0.6 cm) in diameter are set into rotation at speeds of about 230,000 revolutions per minute. In this device, colloidal particles, not much larger than the size of molecules, can be separated from each other.