Search USP29  
Dried Ferrous Sulfate

Sulfuric acid, iron(2+) salt (1:1), hydrate.
Iron(2+) sulfate (1:1) hydrate [13463-43-9].

Anhydrous 151.91 [7720-78-7].
» Dried Ferrous Sulfate contains not less than 86.0 percent and not more than 89.0 percent of anhydrous ferrous sulfate (FeSO4).
Packaging and storage— Preserve in well-closed containers.
Identification— It responds to the tests for Ferrous Salts 191 and for Sulfate 191.
Insoluble substances— Dissolve 2.0 g in 20 mL of freshly boiled dilute sulfuric acid (1 in 100), heat to boiling, and digest in a covered beaker on a steam bath for 1 hour. Filter through a tared filtering crucible, wash thoroughly, and dry at 105: the weight of the insoluble residue does not exceed 1 mg (0.05%).
Arsenic— It meets the requirements of the test for Arsenic under Ferrous Sulfate.
Lead— Using Dried Ferrous Sulfate, proceed as directed in the test for Lead under Ferrous Sulfate: the limit is 0.001%.
Mercury— It meets the requirements of the test for Mercury under Ferrous Fumarate.
Organic volatile impurities, Method IV 467: meets the requirements.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Dissolve about 800 mg of Dried Ferrous Sulfate, accurately weighed, in a mixture of 25 mL of 2 N sulfuric acid and 25 mL of freshly boiled and cooled water. Add orthophenanthroline TS, and immediately titrate with 0.1 N ceric sulfate VS. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N ceric sulfate is equivalent to 15.19 mg of anhydrous ferrous sulfate (FeSO4).
Auxiliary Information— Staff Liaison : Lawrence Evans, III, Ph.D., Scientist
Expert Committee : (DSN05) Dietary Supplements - Non-Botanicals
USP29–NF24 Page 902
Phone Number : 1-301-816-8389