Physical Pharmacy theories of emulsion slide.pdf

Here are three theories of emulsion

1. topic
Theories of Emulsion
Submitted by: Hasham
Submitted to: MaamMamunaYaqoob

2. Emulsion
An emulsion is a mixture of two or more liquids that are
normally immiscible (unmixable or unblendable) owing
to liquid-liquid phase separations

3. Theories of
emulsion
Surface tension theory
Plastic or interfacial film theory
Harkin’s oriented –wedge theory
Theory of viscosity
Fischer theory of hyDrates

4. Harkin’s
oriented –
wedge theory
The oriented wedge theory proposes that the surfactant forms
monomolecular layers around

the droplets of the internal phase of the emulsion. The theory is
based on the assumption that Emulsifying agent orient
themselves about and within a liquid relative to their stability in
that particular liquids

5. Depending on the shape and size of the molecules, their
solubility characteristics, and, thus,
their orientation, the wedge shape theory proposes that
emulsifiers surround either oil
globules or water globules.
An emulsifying agent, having a greater hydrophilic character
than hydrophobic character,
will promote oil in water emulsions.
Conversely, water in oil emulsions result with the use of an
emulsifier that is more hydrophobic than hydrophilic.
In this theory the surfactant emulsifier molecules are
assumed be shaped like wedges;
therefore, it is termed “Oriented wedge

6. Theory of
viscosity
It states that more viscous emulsion the greater is the stability. But
it is not always true.
This theory is holds good for emulsions prepared with gums as
emulsifying agents
Example:
Milk has low viscosity but most stable, O/W emulsion.
Cold Cream is an example of more viscous emulsion, O/W
emulsion

7. Fischer theory
of hydrates
and solvates
FISCHER’S THEORY OF HYDRATES AND SOLVATES:
Fischer’s observed that the use of specific ratios of
emulsifying agent to continuous phase, he claimed that
the quantity of water in these specified ratios was all
used up in forming a colloidal hydrate.
It states that disperse phase form colloidal hydrate or
colloidal complex.
Example:
O/W emulsion, oil form colloidal complex and in W/O
emulsion water form colloidal complex and known as
solvate.