Buoyant density centrifugation
Buoyant density centrifugation (also isopycnic centrifugation or equilibrium density-gradient centrifugation) uses the concept of buoyancy to separate molecules in solution by their differences in density. == Implementation == Historically a cesium chloride (CsCl) solution was often used, but more commonly used density gradients are sucrose or Percoll.
Source: Wikipedia — Buoyant density centrifugation (CC BY-SA 4.0)