The adsorption of polyethylenimine and carboxymethylcellulose sodium s
alts from aqueous electrolyte solutions and its effect on the sediment
ation rate, volume of sediment, electrokinetic potential and degree of
aggregation of homo-disperse polystyrene and melamineformaldehyde cop
olymer particles were investigated. The adsorption isotherms are of hi
gh-affinity type and may be described by the Hesselink theory of polye
lectrolyte adsorption. Starting from the calculated values of the adso
rption layer thickness and the segment densities in polymer coils and
adsorption layers a considerable deformation of polymers during adsorp
tion was assumed. It was shown that the flocculation of suspensions by
polyelectrolytes takes place far from the isoelectric point of partic
les. The role of electrostatic, structural and steric forces in the me
chanism of stabilization of dispersions by oppositely charged polyelec
trolytes is discussed.