Figure 4

Scaled quantities from zeta-potential measurements and SHG for the different solution replacements; a and b: data plotted as a function of measured Al-concentration. In Figure a the SHG data were collected after the step-wise addition of Al; the EKP (electrokinetic potential) data pertain to the first measurement made after replacing the solution (i.e. prior to increasing the pH). In Figure b data pertain to measurements involving removal (i.e. replacement of the solution). Figure 4c shows the replacement data as a function of the number of solution replacement.