Svedberg
A svedberg unit (symbol S, sometimes Sv) is a non-SI unit for sedimentation rate. The sedimentation rate for a particle of a given size and shape measures how fast the particle 'settles', or sediments. It is often used to reflect the rate at which a molecule travels to the bottom of a test tube under the centrifugal force of a centrifuge. The svedberg is technically a measure of time, and is defined as exactly 10−13seconds (100 fs).
The Svedberg unit (S) offers a measure of particle size based on its rate of travel in a tube subjected to high g-force.
It should not be confused with SI unit sievert or the non-SI sverdrup.
Naming
The unit is named after the Swedish chemist Theodor Svedberg (1884–1971), winner of the 1926 Nobel Prize in chemistry for his work on disperse systems, colloids and his invention of the ultracentrifuge.
Factors that affect
The Svedberg coefficient is a nonlinear function. A particle’s mass, density, and shape will determine its S value. It depends on the frictional forces retarding the particle’s movement, which in turn are related to the average cross-sectional area of the particle.
