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Colloidal Dispersion
Dr. Aws AlshamsanDepartment of Pharmaceutics
Office: AA87Tel: 4677363
Dispersion Systems
True Solution
<1nm
Colloidal Dispersion
1nm – 1mm
Coarse Dispersion
>1mm
True Solution Colloidal Dispersion Coarse Dispersion
Visibility None Electronic microscope
Naked eye and optical microscope
Motion Thermal Brownian Gravitational
Separation None Membrane filter Paper filter
Sedimentation None Ultracentrifuge Centrifuge
Optical properties Passes light Tyndall effect Scatters light
Colligative properties High Small None
Properties of colloidal dispersions
Solid Liquid Gas
Solid Zinc oxide paste Suspensions Aerosols
Liquid Butter Emulsion Nasal spray
Gas Solid foam Soda water ---
Classification of dispersed systems
Dispersion Medium
Dis
pers
ed P
hase
Colloids
• Particle size 1 – 1000 nm.• Particles have very large surface area• Homogenous colloidal system - lyophilic
dispersion.• Heterogenic colloidal system – lyophobic
dispersion
Colloids
• Particles are visible only by electron microscope
• Brown motion• Dispersion of passing light (Tyndall efect)• Produce osmotic pressure
Brownian Motion
• The random movement of microscopic and nanoscopic particles suspended in a fluid
Lyophilic colloids
• Dispersion systems are considered lyophilic (solvent-loving) if there is considerable attraction between the dispersed phase and the dispersion medium.
Lyophilic
LipophilicHydrophilic
Lyophilic colloids
• Lyophilic particles are mixed with the suitable solvent. Particles have high affinity to the solvent. –High force of attraction exists between
colloidal particles and liquid. – This result in formation of very stable
system called lyophilic colloidal dispersion
Lyophobic colloids
• Dispersion systems are considered lyophobic (solvent-hating) if there is little attraction between the dispersed phase and the dispersion medium.
Lyophobic
LipophobicHydrophobic
Lyophobic colloids
• Colloid particles do not have affinity to the molecules of solvent
• Complexes of inorganic particles which do not have affinity to the solvent form lyophobic colloids
• They are prepared by artificial dispersion e.g. Fe(OH)3, As2S3
• Emulsions are lyophobic systems
