methods of colloid preparation
DESCRIPTION
Images on dialysis, methods of preparation of colloids, association/ amphiphilic colloids to give students a visual concept and empty slides to be used as cue cardsTRANSCRIPT
COLLOIDS
colloids
Buchner funnel used in ultra filtration
Dialysis
Colloidal gold how color changes with increasing particle size
Methods of preparing colloids
For lyophillic
1. SOLVATION
For lyophobic
Methods for preparing lyophobic colloids
Dispersion
Methods
Condensation or
Aggregation Methods
Dispersion
Methods
Electrical dispersion
Bredig’s Arc Method
Bredig’s Arc Method
Mechanical Dispersion
Colloid mill
Ultrasonic dispersion
High Intensity Ultra sonic generators
Bredig’s Arc Method
High Intensity Ultra sonic generators
Ultrasonic generators
How?
Colloid mill
Colloid mill
Peptisation
Peptisation
Similarly a precipitate of AgCl on shaking with dilute solution of AgNO3, adsorbs Ag+ ion and gets peptised to colloidal particles of type AgCl / Ag+
• Similarly a precipitate of AgCl on shaking with dilute solution of AgNO3, adsorbs Ag+ ion and gets peptised to colloidal particles of type AgCl / Ag+
• Cellulose nitrate is peptised by ethanol. The colloidal solution so obtained is known as Colloidion.
condensation
Supersaturation Chemical reaction
Superaturation
By decreasing temperature
By changing solvent
Process of crystal growth
By change in solvent
Alcohol + sulphur
Supersaturated solution
Excess of water
Nuclei of crystal
Crystal growth
Sulphur colloidal sol
Chemicalreaction
Reduction
Oxidation
• Sulphur
Hydrolysis
• Ferric chloride
• Chromium and Almunium Salts
Double decomposition
• This causes Au3+ ions to be reduced to neutral gold atoms. As more and more of these gold atoms form, the solution becomes supersaturated, and gold gradually starts to precipitate in the form of sub-nanometer particles. The rest of the gold atoms that form stick to the existing particles, and, if the solution is stirred vigorously enough, the particles will be fairly uniform in size.
Association Colloids
Or amphiphilic colloids
amphiphiles
Amphiphilic molecule? Is it colloidal?
Phenomenon of micelle formation
phenomenon
CMC
Aggregation number
In water and in oil
Some shapes
When spherical? When laminar?
Effect on… (surface tension)
Are micelles solid?
In lyophillic sols?
Types of association colloids?
gegenions
Types of Amphiphiles