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Syllabus of Unit 1 :-

Colloidal dispersions : Classification of dispersed systems & their general characteristics, size & shapes of colloidal particles, classification of colloids &comparative account of their general properties. Optical, kinetic & electrical properties. Effect of electrolytes, coacervation, peptization& protective action.

1. Colloidal Dispersion

Dispersed systems incorporates particulate (known because the dispersed phase), distributed throughout a continuous phase (known as dispersion medium).

Classification of Dispersed System :-

On the idea of mean particle diameter of the dispersed material, three styles of dispersed systems are generally considered :-
  1. Molecular dispersions
  2. Colloidal dispersions
  3. Coarse dispersions

A. Molecular dispersions are actuality solutions of a solute innovate a solvent. The solute is within the form of separate molecules homogeneously distributed throughout the solvent. Example: aqueous solution of salts, glucose.

B. Colloidal dispersions are micro-heterogeneous dispersed systems. The dispersed phases can not be separated under gravity or centrifugal or other forces. The particles don't mix or cool down. Example: aqueous dispersion of natural polymer, colloidal silver sols, jelly.

C. Coarse dispersions are heterogeneous dispersed systems within which the form particles are larger than 0.5µm. The concentration of dispersed particles may exceed 20%. Example: pharmaceutical emulsions and suspensions

2. Properties of Colloidal Dispersion

A. Optical Properties of Colloids
a. Tyndall Effect
  • When a beam of sunshine is undergone a colloid kept in dark, the trail of the beam gets illuminated with blue colour.
  • This phenomenon is understood because the Tyndall effect and therefore the path is understood because the Tyndall cone.
  • The Tyndall effect is thanks to the scattering of sunshine by colloidal particles.
  • Tyndall effect isn't exhibited by a real solution. this can be because of the particles within the solution are too small to scatter light.

B. Kinetic Properties of Colloids
b. Brownian Movement
  • The continuous zigzag movement of particles within the dispersing phase during a colloid is termed pedesis.
  • Brownian movement is thanks to the unequal bombardment of the moving molecules of form on colloidal particles.
  • Brownian movement decreases with a rise within the size of the colloidal particles. So suspension doesn't exhibit the pedesis.

C. Electrical Properties of Colloids
  • The movement of colloidal particles towards a selected electrode under the influence of an electrical field.
  • The colloidal particle with a charge moves towards the cathode under the influence of the electrical field and also the colloidal particle with a electric charge moves towards the anode.