What is electro-osmosis?
The medium can move but not the particles; this phenomenon is known as electro-osmosis.
or
When the electrophoresis of dispersed particles in a colloidal system is prevented by some suitable means, it is observed that the dispersion medium itself begins in an electric field. This phenomenon is known as electro-osmosis.
A simple apparatus for studying electro-osmosis is shown in the figure. The colloidal system in central compartment A is placed, separated from compartments B and C, and is filled with water by the dialysing membranes M and M’.
As shown in the figure, the water in compartments B and C extends to the side tubes T and T’.
Electro-osmosis
The membranes prevent the movement of the colloidal particles. Therefore, as shown, the water begins to move when a potential difference is applied across the electrodes held close to the membranes in compartments B and C.
If water is carrying a negative charge and particles have a positive charge. Therefore, it would start moving towards the anode, and the level of water in the side tube T would be seen to rise. On the other hand, the particle carrying a negative charge, and the water carrying a positive charge, will start moving toward the cathode, and the water level in the side tube T’ will begin rising.
