Sedimentation or Dorn Effect

Sedimentation or Dorn Effect

1) We know that the dispersed phase remains suspended in Dispersion medium.

2) It is a two phase system and very stable.

3) But even though these colloidal dispersions are fairly stable, the particles slowly settle down under the influence of gravity when kept undisturbed for a longer period of time.

4) It is a very slow process and is just like falling of a spherical body in highly viscous medium.

5) While settling the heavy particles settle first at the bottom and the light particles at the top.

6) Such settling of the colloidal particles under the influence of an gravity is called as Sedimentation or Dorn Effect.

7) In 1880, DORN observed this phenomenon first ,hence it is known as DORN effect.

8) The Potential developed due to this is called as Sedimentation Potential.

9) Sedimentation Potential can be measured by placing the electrodes at different levels in the falling stream of the colloidal particles.

10) It is just reverse of Electrophoresis i.e in Electrophoresis there is movement of colloidal particles due to an applied potential while in Dorn effect the potential is developed due to movement of colloidal particles.