Grains of sand,most pharmaceutical emulsions and suspension, red blood cells
Types of Colloidal dispersion
Lyophilic colloids
Systems containing colloidal particles that interact to an appreiable extent with the dispersion medium are referred to as lyophilic(solventloving)colloids. hydrophilic sols: gelatin, acacia, insulin, albumin Lipophilic colloids: rubber, polystyrene. A material that forms a lyophilic colloidal system in one liquid(e.g. water) may not do so in another liquid(e.g. benzene).
Colloidal dispersion system
size
class Molecular dispersion
Colloidal dispersion
Coarse dispersion
Particle size Less than 1 nm
From 1 nm to o.5 μm
Greater than o.5 μm
grinding method
sonication dispersion method
arc discharge method
• Owing to the intense heat generated by the arc, some of the metal of the electrodes is dispersed as vapor, which condenses to form colloidal particles.
ultrafiltration
• Electro ultrafiltration
Association colloids
CMC
the critical micelle concentration (CMC) is defined as the concentration of surfactants above which micelles form and all additional surfactants added to the system go to micellห้องสมุดไป่ตู้s.
• FeCl3 （w）+3H2O （H）→ Fe(OH)3 （sol） +3HCl
• 2H2S(w）+ SO2(g) → 2H2O +3S (sol）
• Na2S2O3 +2HCl → 2NaCl +H2O +SO2 +S (sol)
• 2HAuCl4+ 3HCHO +11KOH → 2Au(sol）
Not resolved by ordinary microscope (although may be detected under ultramicroscope) Visible in electron microscope Pass though filter paper Do not pass semipermeable membrane Diffusion very slowly
Lyophobic colloids
Lyophobic colloids is composed of materials that have little attraction. e.g. gold, silver, sulfur, arsenous sulfide, and silver iodide.
Physical condensation methods
1,replacement of solvent
Physical condensation methods
2, Steam quench method
chemical condensation methods
• 2H3AsO3（w）+ 3H2S →As2S3（sol） +6H2O
The methods to prepare lyophobic colloids
•Dispersion methods 1,grinding method 2,sonication dispersion method 3,arc discharge method
•Condensation methods 1,physical methods 2,chemical methods
Sol purification
• 1,dialysis method
• 2,ultrafiltration
dialysis method
•Semipermeable membrane
dialysis method
•Electrodialysis
ultrafiltration
•Semipermeable membrane
Colloidal silver sols, natural and synthetic polymers, cheese, butter, jelly, milk, etc.
Visible under microscope Do not passthough normal filter paper Do not dialyze though semipermeable menmbrane Do not diffusion
Characteristics of system
example
Invisible in electron microscope Pass through ultrafilter and semipermeable membrane undergo rapid diffusion
Oxygen molecules, ordinary ions, glucose