Sedimentation speed of particles in a liquid
Settling - Theoretical aspects

The theory of sedimentation of fine solids in a liquid, which obeys Stokes' law, shows that the falling speed of a particle is proportional to the difference in density between the particle and the liquid, and to the square of the particle's size. Consequently, any phenomenon likely to increase particle diameter promotes sedimentation very significantly, so that flocculation has become an intrinsic part of sedimentation. Most materials suspended in a liquid are naturally flocculated and can therefore be concentrated by sedimentation, albeit sometimes very slowly.