Lab Final - Emulsions

• 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

• internal/discontinuous phase: dispersed liquid
• external/continuous phase: dispersion medium

• o/w - external is water and internal is oil
• w/o - external is oil and internal is water

• hydrophilic
• HLB (8-18)

• hydrophobic
• HLB (3-6)

• surfactants
• surface actives
• wetting agents

• stable mix of two immiscible liquids
• administration of unplatable oil
• increased absorption
• admin of irritant drugs to the skin

• surface tension
• oriented wedge
• plastic or interfacial film

interfacial tension is lowered (tension between two different phases

when a single layer of emulsifying agent wraps around the dispersed/internal phase to form a micelle

film of emulsifying agent prevents contact and coalescing of the dispersed phase

• hydrophil-lipophil balance
• indicates the polarity of the substance
• usual range - 1-20

• more hydrophilic
• more hydrophobic

• creaming
• coalescence
• phase inversion

dispersed oil droplets merge and rise together (can be easily re-dispersed by shaking)

• breaking or cracking - 
• complete fusion of the dispersed phase (irreversible)

changing from w/o to o/w or vice versa (irreversible)

• particle size
• density difference
• viscosity

determined by Stoke's law

• bottle (Forbes) method
• syringe method
• stir bar method
• homogenizer method