Dialysis of Lyophilic and Lyophobic Sol

Introduction

• Lyophilic Sols: "Liquid loving" sols where dispersed phase and dispersion medium have strong attraction, e.g., starch in water.
• Lyophobic Sols: "Liquid hating" sols with little or no attraction between dispersed phase and dispersion medium, e.g., ferric hydroxide sol.

Differences Between Lyophilic and Lyophobic Sols

• Lyophilic Sols:
  • Strong affinity for dispersion medium
  • Stable and reversible
  • No charge on colloidal particles
  • No stabilizers needed
  • Solvent loving (e.g., hydrophilic when water is solvent)
  • Highly viscous
  • Examples: Starch sol, egg albumin sol
• Lyophobic Sols:
  • Little or no affinity for dispersion medium
  • Less stable and irreversible
  • Carry positive or negative charge
  • Require stabilizers
  • Solvent hating
  • Similar viscosity to solvent
  • Examples: Ferric hydroxide sol, aluminium hydroxide sol

Dialysis of Sols

Aim

• Purify lyophilic and lyophobic sols by removing compounds causing instability.

Materials Required

• Parchment or cellophane paper, iron stand, trough, thread, test tubes, egg albumin sol, distilled water, silver nitrate, uranyl zinc acetate.

Theory

• Dialysis is used to purify sols by separating impurities using a parchment membrane.

Procedure

1. Wash and dry test tubes and trough.
2. Prepare parchment or cellophane paper cone.
3. Fill cone with egg albumin sol.
4. Suspend the cone in a trough filled with distilled water.
5. Change water in trough every 30 minutes until impurity-free.
6. Test for ions using uranyl zinc acetate and silver nitrate.
7. Note time taken for purification.

Result

• Time for dialysis of egg albumin sol is recorded.

Precautions

• Ensure airtight parchment bag.
• Keep parchment cone above water surface.
• Change trough water timely.

Viva Questions

• Lyophilic Sol: Strong attraction between dispersion medium and phase.
• Lyophobic Sol: Little or no attraction.

Examples

• Lyophilic Sols: Gum sol, starch sol, rubber, gelatin, egg albumin sol.
• Lyophobic Sols: Ferric hydroxide sol, aluminium hydroxide sol, arsenious sulfide sol.

FAQs

• Why use parchment paper?
  • Colloidal particles can’t pass through; ions can.
• Why airtight parchment cone?
  • Prevents water entry.