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Lab Final - Emulsions
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emulsion definition
thermodynamically unstable
two phase system of at least two immiscible liquids and emulsifying agents
one of the liquids is dispersed in the form of small droplets throughtout the other
two emulsion phases and their definitions
internal/discontinuous phase
: dispersed liquid
external/continuous phase
: dispersion medium
types of emulsion phases and their internal and external phases
o/w - external is water and internal is oil
w/o - external is oil and internal is water
emulsifier for o/w phase and the HLB
hydrophilic
HLB (8-18)
emulsifier for w/o phase and the HLB
hydrophobic
HLB (3-6)
what can act as an emulsifier
surfactants
surface actives
wetting agents
advantages of emulsions
stable mix of two immiscible liquids
administration of unplatable oil
increased absorption
admin of irritant drugs to the skin
theories of emulsification
surface tension
oriented wedge
plastic or interfacial film
Surface Tension theory
interfacial tension is lowered (tension between two different phases
orient wedge theory
when a single layer of emulsifying agent wraps around the dispersed/internal phase to form a micelle
plastic/interfacial film
film of emulsifying agent prevents contact and coalescing of the dispersed phase
what is the HLB? what is the usual range?
hydrophil-lipophil balance
indicates the polarity of the substance
usual range - 1-20
a higher HLB means what?
a lower HLB means what?
more hydrophilic
more hydrophobic
HLB equation
types of instabilities
creaming
coalescence
phase inversion
what is creaming?
dispersed oil droplets merge and rise together (can be easily re-dispersed by shaking)
what is coalescence?
breaking or cracking -
complete fusion of the dispersed phase (irreversible)
what is phase inversion
changing from w/o to o/w or vice versa (irreversible)
what is the rate of separation related to?
particle size
density difference
viscosity
determined by Stoke's law
methods of preparation
bottle (Forbes) method
syringe method
stir bar method
homogenizer method
Author
jcu1
ID
212660
Card Set
Lab Final - Emulsions
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Lab Final
Updated
4/15/2013, 12:30:34 AM
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