ABSTRACT
Introductory descriptions of surface charging and the electrical double layer can be found in numerous handbooks of surface and colloid chemistry (e.g., [4-7]), in other books (e.g., [8-10]), and in review articles (e.g., [11]). The reader of the present book is assumed to be familiar with these phenomena and with basic ideas and methods of analytical chemistry. Figures 1.1 and 1.2 show the idealized picture as presented in the handbooks. The s0(pH) curves obtained at different concentrations c1 < c2 < c3 of an inert 1-1 electrolyte shown in Figure 1.1 have a common intersection point (CIP) at s0 = 0. The absolute value of s0 at constant pH increases as the ionic strength increases on the both sides of the point of zero charge (PZC). s0 at constant ionic strength steadily decreases as pH increases. Many examples of such sets of three or more charging curves are reported in the literature. The number of charging curves shown in Figure 1.1 is limited to three for clarity. Differences between c1, c2, and c3 by an order of magnitude are necessary to obtain a clear difference in the absolute value of s0 and a clear CIP. When the differences between the concentrations are smaller, the charging curves obtained at various ionic strengths are likely to overlap rather than intersect. The z(pH) curves obtained at different concentrations c1 < c2 < c3 of an inert 1-1 electrolyte shown in Figure 1.2 show a common IEP. The absolute value of z at constant pH decreases as the ionic strength increases on both sides of the IEP. z at constant ionic strength steadily decreases as pH increases.
