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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 0.5┬Ám. 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.