An emulsion is a mixture of two immiscible liquids, where one liquid is dispersed as globules in the other. There are two types: oil-in-water (O/W) and water-in-oil (W/O). Emulsions have advantages like masking unpleasant tastes and sustained drug release, but are thermodynamically unstable with a short shelf life. Emulsions contain a dispersed internal phase and a continuous external phase, and emulsifying agents are used to stabilize the emulsion by reducing interfacial tension at the boundary between the two liquids.

1. Emulsion
Sarder Istiaque Ahmed
111-29-308
Daffodil International University

2. • A mixture of two or more liquids that are
normally Immiscible.
• One liquid phase is dispersed is dispersed as
globules in the other liquid phase.

3. Advantages
• Mask the unpleasant taste.
• Sustained
release medication.
• Inert and chemically non-
reactive.
• Reasonably odorless and
cost effective.
Disadvantages
• Thermodynamically
unstable and have short
shelf-life.
• Leads to creaming and
cracking .
• leads to phase inversion.

4. Phase in Emulsion
• The dispersed liquid is known as the Internal
or Discontinuous phase.
• The dispersion medium is known as the
External or Continuous phase.

5. Types Of Emulsion
Oil in Water (O/W)
Water in Oil (W/O)
Water in Oil in water emulsion.
 Based on size of liquid droplets:
 Macroemulsions (0.2 – 50 mm)
Microemulsions (0.01 – 0.2 mm)

6. Identification Tests For Emulsion
 Dye test.
 Dilution test.
 Electrical conductivity test.
 Fluorescence test.
 Cobalt chloride test.

7. Emulsifying Agent
• Soluble in both oil and water and enable oil to be uniformly
dispersed in water as an emulsion.
• Emulsifying agents can be classified according to:
 1) Chemical structure:
 Synthetic Emulsifying Agents (Sodium stearate, Benzalkonium
chloride).
 Natural Emulsifying Agents (Acacia, Tragacanth, Gelatin)
 Finely Dispersed Solids (Bentonite, Veegum)
 Auxilary Agents
 2) Mechanism of action:
 Monomolecular
 Multi-molecular
 Solid particle films.

8. HLB Value
• The hydrophilic-lipophilic balance of a surfactant is a
measure of the degree to which it
is hydrophilic or lipophilic.
• Has an arbitrary scale of 1 - 18.
• Low HLB Indicates?
Low number of hydrophilic groups on the Molecule
thus imparting Lipophilic character. E.g. Spans have low
HLB numbers.
• High HLB indicates?
Emulsifier has a large number of hydrophilic groups on
the molecule thus imparting hydrophilic Character. E.g.
Tweens have higher HLB numbers

9. Theories Of Emulsification
• Electric double layer theory.
• Phase volume theory.
• Hydration theory of emulsions.
• Adsorbed film and interfacial tension theory.
Figure: Electric Double Layer

10. Figure: Interfacial Tension Theory
Figure: Surface Tension

11. Methods Of Preparation Of Emulsion
1) Dry Gum Methods
2) Wet Gum Methods
3) Bottle Method
4) Beaker Method.
5) In situ Soap Method.

12. Instability