Study Set Content:
Is a thermodynamically unstable system consisting of at least two immiscible liquid phases, one of which is dispersed as globules in the other liquid phase, stabilized by the presence of an emulsifying agent
emulsions
TYPES OF EMULSIONS' based on Dispersed phase
W/O
O/W
(water is dispersed as globules in the oil continuous phase)
W/O
(oil droplets are dispersed throughout the aqueous phase)
O/W
(0.2 – 50 mm macroemulsions)
Kinetically stable
(0.01 0 0.2 mm microemulsions)
Thermodynamically stable
Pharmaceutical Emulsions
a. Lotions
b. Liniments
c. Creams
d. Ointments
e. Vitamin drops
By lowering of interfacial tension
Surface Tension Theory
Monomolecular layers of emulsifying agents are curved
around a droplet of the internal phase of the emulsion
Oriented Wedge Theory
A film of emulsifying agent prevents the contact and
coalescing of the dispersed phase.
Interfacial Film Theory
introduced the use of acidic
constants for the ionization of bases
in 1923
Bronsted
realized the advantage of expressing
the ionization of acids and bases on
the same scale, just as pH value can
denote both alkalinity and acidity
Bronsted
< 7.00
acidic
> 7.00
Basic
7.00
Neutral
[H
+
] (M)
> 1.0 x 10-7
Acidic
< 1.0 x 10
-7
Basic
[OH
-
] (M)
< 1.0 x 10-7
Acidic
> 1.0 x 10-7
Basic
drugs that are weak electrolytes
Drugs as buffer
