Ferric Oxide USP NF
Ferric Oxide contains not less than 97.0 percent and not more than 100.5 percent of Fe2O3, calculated on the ignited basis.

Identification: Dissolve 0.5 g in 50 mL of hydrochloric acid, and dilute with water to 200 mL: the solution so obtained responds to the test for Ferric Salts under Iron..
Water-soluble substances: Digest 2.0 g in 100 mL of water on a boiling water bath for 2 hours, filter, and wash the filter with water. Evaporate the filtrate and washings, and dry the residue at 105 for 1 hour: the weight of the dried residue is not more than 20 mg (1.0%).
Acid-insoluble substances: Digest 2.0 g in 25 mL of hydrochloric acid by boiling for 20 minutes. Add 100 mL of hot water, and filter quantitatively through a tared filtering crucible, with the aid of hot wash water, until the filtrate tests negative for chloride. Dry the crucible and contents at 105 for 1 hour: the residue weighs not more than 6 mg (0.3%).
Organic colors and lakes: Place 1.0 g in each of 3 beakers, and add 25 mL of each of the following reagents, respectively: 1-chloronaphthalene, alcohol, and chloroform. Heat the beakers containing alcohol and chloroform just to boiling. Heat the other beaker on a boiling water bath for 15 minutes, with occasional swirling. Filter the contents of the beakers through retentive, solvent-resistant filter paper. If any of the filtrates shows visible turbidity, centrifuge for 15 minutes. Record the spectra against respective solvent blanks in 1-cm cells from 350 to 750 nm. No peak, above the noise level, with a slope greater than +0.001 absorbance unit per nm is found.
Mercury: The limit is 3 µg per g.
Limit of arsenic: The limit is 3 µg per g.
Limit of lead: The limit is 0.001%. (0.001%).