An Experimental Test of the Ion Condensation Theory for Spherical Colloidal Particles.

This paper deals with the notion of ion condensation for spherical colloids and, more specifically, with a recent model developed to predict effective charges (Y. Levin, M. C. Barbosa, and M. N. Tamashiro, Europhys. Lett. 41, 123, 1998). Electrophoretic mobility measurements (carried out for a set of well-characterized latexes) were used to find out to what extent this theory is able to accounts for: (i) the insensitivity of mobility to surface charge, and (ii) the small values of electrokinetic charge found at low ionic strength. As the Levin theory was developed assuming no added salt, a previous discussion about the effect of additional electrolyte was needed. Contrary to what other authors have reported, our results do not support the above-mentioned theory. Copyright 2001 Academic Press.