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Physical condensation methods
1,replacement of solvent
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Physical condensation methods
2, Steam quench method
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chemical condensation methods
• 2H3AsO3（w）+ 3H2S →As2S3（sol） +6H2O
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 di.ffusion
• 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） .
Grains of sand,most pharmaceutical emulsions and suspension, red blood cells
Types of Colloidal dispersion
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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).
Characteristics of system
example
Invisible in electron microscope Pass through ultrafilter and semipermeable membrane undergo rapid diffusion
Oxygen molecules, ordinary ions, glucose
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ultrafiltration
• Electro ultrafiltration
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Association colloids
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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 micelles.
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grinding method
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sonication dispersion method
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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.
Colloidal dispersion system
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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
.
.
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Lyophobic colloids
Lyophobic colloids is composed of materials that have little attraction. e.g. gold, silver, sulfur, arsenous sulfide, and silver iodide.
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
Sol purification
• 1,dialysis method • 2,ultrafiltration
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dialysis method
•Semipermeable membrane
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dialysis method
•Eln
•Semipermeable membrane
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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