1. Colloidal Dispersion Dr. Aws Alshamsan Department of Pharmaceutics Office: AA87 Tel: 4677363 aalshamsan@ksu.edu.sa

2. Dispersion Systems True Solution <1nm Colloidal Dispersion 1nm – 1  m Coarse Dispersion >1  m

3. True Solution Colloidal Dispersion Coarse Dispersion VisibilityNone Electronic microscope Naked eye and optical microscope MotionThermalBrownianGravitational SeparationNoneMembrane filterPaper filter SedimentationNoneUltracentrifugeCentrifuge Optical propertiesPasses lightTyndall effectScatters light Colligative properties HighSmallNone Properties of colloidal dispersions

4. SolidLiquidGas Solid Zinc oxide paste SuspensionsAerosols LiquidButterEmulsionNasal spray GasSolid foamSoda water--- Classification of dispersed systems Dispersion Medium Dispersed Phase

5. Colloids Particle size 1 – 1000 nm. Particles have very large surface area Homogenous colloidal system - lyophilic dispersion. Heterogenic colloidal system – lyophobic dispersion

6. Colloids Particles are visible only by electron microscope Brown motion Dispersion of passing light (Tyndall efect) Produce osmotic pressure

7. Brownian Motion The random movement of microscopic and nanoscopic particles suspended in a fluid

8. Lyophilic colloids Dispersion systems are considered lyophilic (solvent-loving) if there is considerable attraction between the dispersed phase and the dispersion medium. LyophilicLipophilicHydrophilic

9. 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

10. Lyophobic colloids Dispersion systems are considered lyophobic (solvent-hating) if there is little attraction between the dispersed phase and the dispersion medium. LyophobicLipophobicHydrophobic

11. 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, As 2 S 3 Emulsions are lyophobic systems