The stability of pyrogenic tungsten trioxide hydrosols is studied in the pr
esence of various monovalent cations between pH 2 and 12. The hydrosol crit
ical coagulation concentrations (c*) are determined by extrapolation of the
experimental log W-log c curves up to log W = 0. The c* of K (+), Rb (+) a
nd Cs (+) slightly increase with the pH of the solution while the c* of Li
(+) presents a pronounced maximum at pH 4.5. A less marked maximum is also
observed at the same pH in the presence of Na (+). The corresponding ionic
adsorption sequence at the water-WO3 interface deduced from these experimen
tal data is Cs (+) > Rb (+) > K (+) > Na (+) > Li (+) in the pH domain unde
r investigation. This overall behavior is successfully explained by the mod
el proposed by Gierst who has generalized the Gurney concept describing the
ion-ion interactions in solution to the ion-surface interactions. The resu
lts reported in this work are also compared with those obtained previously
for other oxides; they confirm the validity and the generality of the concl
usions already drawn concerning the ionic adsorption sequences at the oxide
-water interface. (C) 1999 Elsevier Science B.V. All rights reserved.