Page 68 - Statistics presented by Dr. Sara Ismail Aborass

9/8/2023

d)Coprecipitation by surface adsorption
Ions are adsorbed from the mother liquor

on the surface of ppted particles
Surface adsorption is specially significant

for colloidal particles
Ex: Al(OH)3
Elimination: Washing

Digestion, reprecipitation, elimintion

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Homogenous precipitation
If the precipitating agent is generated
slowly throughout the system at the
same time by a homogenous chemical
reaction, the rate of supersaturation
will not be high, lead to formation of
crystalline pure ppt
Occlusion and surface adsorption are
less liable to occur because the time is
enough for the adsorbed contaminants
to be replaced by lattice ions

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