2. Emulsions
Colloidal solution of two or more immiscible liquids
In emulsion formation droplets on one liquid are
dispersed into other liquid
Components of Emulsion
Inner phase/discontinuous phase/dispersed phase
The liquid being dispersed into other liquid
Outer phase/continuous phase/dispersion
medium
The liquid in which other liquid is dispersed
Stability of emulsion may range from few minutes
to few years
Emulsification ( Lecture #01)
3. Emulsification
Process of formation of emulsions
It is the most versatile property of surfactants
e.g. Paints, medicinal syrups, cosmetics, ice
creams, pesticides, polishes, metal cleaners,
metal cutting oils, textile processing oils, milk,
tea whitener, chocolate drinks.
Above products are either emulsions or used in
emulsified forms.
Emulsification ( Lecture #01)
4. Emulsification ( Lecture #01)
Types of emulsions
Emulsions are of four types
(i) Macroemulsions (ii)Microemulsions
(iii) Nanoemulsions (iv) Multiple emulsions
Macroemulsion
In these emulsions particle size of dispersed
phase is greater than 400nm(0.4μm).
These emulsions are opaque and their particles
are visible under microscope.
5. Emulsions
Microemulsions
In these emulsions particle size of dispersed phase is less
than 100nm(0.1μm).
These emulsions are transparent, and their particle are
not easily visible under microscope
Nanoemulsions
In these emulsions particle size of dispersed phase ranges
from 100 to 400nm. It is also called miniemulsion.
Multiple emulsions
In these emulsions dispersed phase is also emulsion (not
pure liquid). Multiple emulsion is produced by adding an
emulsion into dispersion medium.
Emulsification ( Lecture #01)
6. Pure immiscible liquids do not form emulsion.
For stable emulsion a third component must be added.
It is called emulsifier or emulsifying agent (mostly
surfactant)
The most effective emulsifiers are mixture of two or
more surfactants.
PURITY IS LITTLE REQUIRED IN NATURE
`
Emulsification ( Lecture #01)
7. Macroemulsions
Particle size >400 nm
According to nature of dispersed phase macroemulsions are of
Two types
(i) Oil in Water (O/W) macroemulsions and
(ii) Water in oil (W/O) macroemulsions
Word “oil” is used for nonpolar liquid irrespective of its nature
O/W Macroemulsion
Oil is used as discontinuous phase (inner phase) and water is
being used as continuous phase (outer phase)
W/O macroemulsion
Water is used as discontinuous phase (inner phase) and oil is
being used as continuous phase (outer phase)
Emulsification ( Lecture #01)
8. Bancroft rule
More water soluble emulsifiers favour formation
of o/w emulsions while more oil soluble
emulsifiers favour formation of w/o emulsions.
O/W and W/O emulsions are not in
thermodynamic
equilibrium with each other. One of them is
usually more stable than the other.
Stability depends on nature of emulsifying
agent, volume of oil(non polar liquid) and water
being added, temperature and other
experimental conditions.
Emulsification ( Lecture #01)
9. Inversion of emulsions
O/w and w/o macroemulsions can be can be
converted to the other by changing conditions.
Emulsification ( Lecture #01)
10. Differentiation between o/w and w/o macroemulsions
S# Properties O/W emulsions W/O emulsions
01 Dilution Can be diluted by adding water Can be diluted by adding oil
02 Electrical
conductivity
Similar to that of water Almost nonconductor of
electricity
03 Colour Can develop colour with water
soluble dyes
Can develop colur with oil
soluble dyes
04 Refractive
index
Close to that of water Close to that of oil
05 Filter paper
test
A drop of an O/W emulsion can
instantly wet the paper
A filter paper impregnated with
20% cobaltous chloride (and
dried) develops pink colour with
o/w emulsions
A drop of an W/O emulsion
cannot wet the paper
No change in colour with W/O
emulsions
Emulsification ( Lecture #01)
