Dried Ferrous Sulfate
FeSO4·xH2O

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 86.0percent and not more than 89.0percent of anhydrous ferrous sulfate (FeSO4).
Packaging and storage— Preserve in well-closed containers.
Identification— It responds to the tests for Ferrous Salts á191ñand for Sulfate á191ñ.
Insoluble substances— Dissolve 2.0g in 20mLof freshly boiled dilute sulfuric acid (1in 100),heat to boiling,and digest in a covered beaker on a steam bath for 1hour.Filter through a tared filtering crucible,wash thoroughly,and dry at 105:the weight of the insoluble residue does not exceed 1mg (0.05%).
Arsenic— It meets the requirements of the test for Arsenicunder Ferrous Sulfate.
Lead— Using Dried Ferrous Sulfate,proceed as directed in the test for Leadunder Ferrous Sulfate:the limit is 0.001%.
Mercury— It meets the requirements of the test for Mercury under Ferrous Fumarate.
Organic volatile impurities,Method IVá467ñ: meets the requirements.
Assay— Dissolve about 800mg of Dried Ferrous Sulfate,accurately weighed,in a mixture of 25mLof 2Nsulfuric acid and 25mLof freshly boiled and cooled water.Add orthophenanthroline TS,and immediately titrate with 0.1Nceric sulfate VS.Perform a blank determination,and make any necessary correction.Each mLof 0.1Nceric sulfate is equivalent to 15.19mg of anhydrous ferrous sulfate (FeSO4).
Auxiliary Information— Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(DSN)Dietary Supplements:Non-Botanicals
USP28–NF23Page 822
Phone Number:1-301-816-8389