5. Suspensions of clay sized FeOOH in 0.001 M NaCl were adjusted over a range of pH with NaOH and HCl, then shaken and allowed to settle in test tubes. One day later, light transmittance through the undisturbed supernatant was measured. The results were as follows:

pH	4.18 4.64 5.06 5.88 6.88 7.28 7.75 8.54 8.74
Transmittance (%)	9.4 21.4 41.9 70.2 91.5 88.0 59.8 57.6 49.5

1. Explain the results based on surface charge
2. What is the PZC of the oxide based on the experiment (think about flocculation and dispersion)