Study Set Content:
If the particles repel each other strongly, the dispersion will
resist coagulation and the dispersed system will be
stable
If the reputation is not sufficient then (blnak)will take place.
coagulation
Electrolytes (ionic substance) act as flocculating agents by
reducing electrical barrier between particles by decreasing xeta
potential and forming bridge between adjacent particles.
Controlled Flocculation
Improve dispersion by reducing surface tension.
o Act as wetting and deflocculating agent
Surfactant
sometime cause flocculation
Ionic surfactant (SLS)
Act as flocculating agent
Polymer
Chain of polymer absorb on multiple particles
o Ex.
▪ Xanthum gum
Polymer
Raising temperature leads to flocculation of sterically stabilized
(by) suspension
nonionic surfactant)
depend upon amount of surfactant absorbed on
particles.
Repulsion force
On heating energy of repulsion reduces because of dehydration
of surfactant, attraction increases and particles
flocculate
particle overcome repulsive barrier
due to ice formation.
During freezing processes
Particles come close enough and experience attractive force
like in primary minimum and form aggregates as per
DLVO
theory.
Fluctutation in temperature changes in particle size distribution
in suspension.
Oswald ripening
Particle growth is common if solubility is temperature
dependent
When temperature is high, small particles dissolve to form
saturated solution
When temperature reduces solute deposit on
large crystals
Polymer PVP segment absorb on drug
acetaminophen
Oswald ripening can be reduced by adding
polymer or surfactant
present around polymer molecule
hydration sheath
Polymer inhibit approach of drug molecule from solution to crystal surface for
deposition
