Fig. 3. (a) X-ray diffraction patterns of the solid-phase precipitates collected after 60 min of reaction time for 0.04 M and 0.10 M [Cl^–] treatments, and (b) corresponding plots of base added during the precipitation reactions. Reactions contained 9.1 mM Cu(II) and Fe(II) and were performed at pH 5.2 ± 0.2 in water.