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)
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