What are the properties of colloid?

1. Brownian movement

• It is the continuous, rapid and haphazard movement of colloid particles in solution due to the uninterrupted buffeting on colloid particles provided by solvent molecules.
• It is a sort of perpetual game of molecular billiards.
• It is seen under ultra microscope.

* In fact all particles in solution are in movement, but it is only the  movement of colloid, particles which is uisually perceptible. Movement of particles bigger than colloid is too slow (due to big size) and the movement of crystalloid is too fast (due to small size) to be uisually perceptible. Colloid particles move in a moderate rate because of its moderate size, so its
movement is visible.

2. Tyndall phenomenon (optical phenomenon)

• When a beam of light is passed through a colloidal solution and observed at right angle, the tract of light becomes visible as white line due to the dispersion of light rays by the colloid particles.

* In true solution this phenomenon is not true, so true solution is regarded as optically clear.

3. Electrical phenomenon

• They carry electric charge (Positive or negative)
• They have a definite isoelectric pH at which they behave as zwitter ion, become less soluble and may precipitate out.
• They undergo electrophoresis by which colloid particles are separated from each other.

 4. Surface phenomenon

• Colloid particles have larger surface area per unit mass.
• They show increased phenomenon of adsorption and interfacial tension.

* In true solution there is no surface phenomenon because here there is no separating surface between solute and solvent as it is a homogeneous solution. In suspension there is less (negligible) surface phenomenon because here solutes are very large and. have lower surface area per unit mass.

5. Non dialyzable.
 

6. Salting out.

• Colloid particles can be allowed to precipitate out of solution by adding appropriate salts to the solution.