"Our age is... a practical one. It demands of us all clear and tangible results of our work"
Theodor Svedberg, chemist
The centrifuge has been around since the mid-1800s. It is a device for separating a precipitate from a solution by spinning it at high speeds (the increased gravitational force means that anything suspended in the solution is forced to the bottom of the container much faster than if left to settle naturally). The first centrifuges were hand-driven, reaching speeds of 800 revolutions per minute (rpm). The first ultracentrifuge, developed by Swedish chemist Theodor Svedberg (1884-1971) in 1924, could rotate at speeds of up to 160,000 rpm, meaning it was capable of exaggerating gravity 1,100,000 times. In his first tests, Svedberg separated hemoglobin from blood in about six hours; using normal gravity it would have taken 180 years.
The device's speed makes it a powerful analytical tool. It can measure a molecule's weight, size, shape, and density. It measures the movement of molecules at a certain rotational speed and this "sedimentation rate" is used to calculate the Svedberg unit (the velocity of the molecule per unit of gravitational field); this is used to work out the molecule's weight.
Svedberg used his new technique to support the theories of Brownian motion put forward by Einstein and Von Smoluchowski, winning him the Nobel Prize in 1926. Nowadays, the ultracentrifuge proves useful for analyzing large molecules while still in solutions similar to those they naturally occur in.
