svedberg or Svedberg unit 

A unit of time, = 0.000 000 000 000 1 second (10⁻¹³, ten trillionths of a second in American-style big numbers), used to measure the sedimentation velocity of colloidal solutions in an ultracentrifuge. Symbol, S. It was first used in 1942

A related unit, the Svedburg flotation unit, has the same value but is used to describe molecules that float rather than sink in the centrifuge, such as lipoproteins. Symbol Sf.

The svedberg is named for T. Svedberg (1884–1971), the Swedish chemist who pioneered use of the ultracentrifuge.²

1. Wilbur B. Bridgman.
Some physical chemical characteristics of glycogen.
Journal of the American Chemical Society, volume 64, number 10 (October 1942).

Page 2350: “The average values of s20 for these ten experiments varied from 60 to 70 S (one Svedberg unit, S, = 1 × 10−13 c.g.s. units).”

2. T. Svedberg and K. O. Pedersen.
The Ultracentrifuge.
New York: Oxford University Press, 1940.

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