8.10 preparation and purification of colloids. 1)low solubility 2)low concentration 3)stabilizing...
TRANSCRIPT
1) preparation
dispersion method
condensation methodThe intrinsical diameter of colloids is 10-9 ~ 10-7 m.
Condensation method: by building up the particles from
single molecules.
Dispersion method: by disintegrating down the bulk
material to the colloidal particles.
condensation method / aggregation method
Chemical condensation:
1) reduction: AgNO3 + tannin + K2CO3
2) oxidation: H2S + SO2
3) hydrolysis: FeCl3 + boiling water
4) precipitation equilibria: AgNO3 + KI; NaSiO3+HCl
Physical condensation:
1) exchange of solvent: sulfur/alcohol sulfur / water
2) condensation of vapor: hydrosol of Hg, Na sol in benzene
Dispersion methods:
colloid millCoarse dispersion
1) colloid mill: mechanical dispersion 2) arc method: 3) ultrasonic method: 4) peptization method:
Bredig’s arc method
Ultrasonic generator
Piezoelectric device
Fe(OH)3 precipitation Newly formed can be peptized by FeCl3 solution and form Fe(OH)3 sol.
2) purification
(1) Dialysis and electrodialysis
Parchment membrane
Dialysing membrane
2) ultrafiltration