Electro-Osmosis
Electroosmosis was first observed by a Russian scientist F.F.
Reuss in 1809.
1) We know that a COLLOID is a substance which is
microscopically dispersed (widely spread) evenly throughout another substance.
2) The Colloidal particles form Dispersed phase and the
medium used for this is called as Dispersion medium.
3) Also we all know that Electrophoresis is a phenomenon in
which the colloidal particles move under the influence of an electric field.
4) But,Suppose if it happens that, the colloidal particles
are not allowed to move under the influence of an electric field, then What
Will Happen...?
Nothing but.....
The dispersion medium itself will begin to move under the
influence of the electric field.
5) This movement of the dispersion medium under the
influence of an electric field is called as "Electroosmosis" .
6) The pressure required to counter the Electro osmotic flow
is called as Electroosmotic pressure.
7) To study the Phenomenon of Electroosmosis consider the
experimental setup as shown in the figure below:-
8) The colloidal solution(sol) is taken in X-compartment
whereas the Y and Z compartments are filled with Dispersed medium,here water is
taken as dispersion medium
9) The X compartment is seperated from Y and Z compartments
by a semipermeable membrane or a porous partition.
10) A positive and a negative
electrode is immersed in the Y and Z compartments as shown in the
figure.
11) When a potential is applied at the electrodes the
dispersion medium will move from one side to other which can be observed on the
basis of the movement of the boundries in the side tubes.
12) The direction of the movement of dispersion medium will
be opposite to the direction of flow of the colloidal particles ,i.e., if
colloidal particles are positively charged then the dispersion medium moves
towards the negative electrode and vice versa.
13) The Zeta Potential developed due to electroosmosis is
given by :-
PÏ€r2 /2DE
Where,
P = Electroosmotic pressure in N/m2
r = radius of side tube in cm
E = Potential applied
D = Dielectric constant of medium
0 comments:
Post a Comment