Preparation: |
ferric hydroxide was first precipitated by adding 3.75 g FeCl3 ∙ 6H2O to 10 mL 4 M NaOH solution while vigorously stirring followed by pH adjustment to 5.0 ± 0.2 using dilute HCl; 10 milliliter aliquots of the slurry were transferred to borosilicate glass ampoules; headspace of at
least 1/3 of the total ampoule capacity was left to allow for safe pressure; ampoules were then sealed and heated at 130 °C for 48 h; freeze dried, ground, and then sieved (45-μm) before use |