Solutions - Emulsions

Question 1

Emulsion def.

Answer 1

Dispersions of one liquid into another that doesn;t form spontaneously

Question 2

Types of emulsion

Answer 2

O/w, w/o, o/w/o
Tests - miscibility tests = mix with continuous phase
(w/O, o/W)
- Conduction = o/w readily conducts electricity
- Staining tests = water/oil soluble dyes

Question 3

Avoid creaming

Answer 3

Creaming - dispersed droplets separating under gravitational influence
Reduce droplet size, increase viscosity, reduce density difference, dispersed phase conc.
Prevent flocculation/coalescence
w/o bottom, o/w top

Question 4

Flocculation def.

Answer 4

Weak reversilbe attraction between droplets forming floccules
Dispersed by agitation
Cream more quickly

Question 5

Coaslescence def.

Answer 5

irreversible merging to form large droplets

Question 6

Cracking def

Answer 6

Complete split of molecules

Question 7

Emulsions stablity methods

Answer 7

Add surfactants
ionic - increase surface charge and repulsive forces
Non-ionic - solvated layer, steric repulsion

Question 8

Mixed surfactant HLB

Answer 8

Hydrophilic lipophilic balance
1-20, polar:non-polar
HLBmix=fHLBa-(1-f)HLBb
mix of hydrophilic and lipophilic give stable emulsions

Question 9

Control of rheological properties

Answer 9

dispersed phase conc
Radius of dispersed pahase
Continupus phase viscosity
Surfactant emulsifier

Question 10

Emulsifying agents

Answer 10

Surfactants/finely divided solids - adsorb at immiscible interfaces
Hydrophilic colloids - form viscoelastic layer

Question 11

Rate of creaming tests

Answer 11

Ratio of volume creamed:total volume
Change in size of globules
Viscosity changes