FeSO4·7H2O 278.02

Sulfuric acid,iron(2+)salt (1:1),heptahydrate.
Iron(2+)sulfate (1:1)heptahydrate [7782-63-0].

Anhydrous 151.91 [7720-78-7].

Packaging and storage— Preserve in tight containers.

Labeling— Label it to indicate that it is not to be used if it is coated with brownish yellow basic ferric sulfate.

Identification— It responds to the tests for Ferrous Salts á191ñand for Sulfate á191ñ.

Arsenic,Method Iá211ñ— Transfer 1.0g to a round-bottom,100-mLflask fitted with a glass joint,add 40mLof 9Nsulfuric acid and 2mLof potassium bromide solution (3in 10),and immediately connect the flask to a condenser having a matching glass joint and a reservoir with a water jacket that is cooled by ice-water.Heat the flask gently over a low flame until the solid dissolves,then distill until 25mLof distillate collects in the reservoir.Transfer this distillate to the arsine generator flask,and wash the condenser and the reservoir with several small portions of water,adding the washings to the generator flask.Swirl to mix,add bromine TSuntil the color of the solution is slightly yellow,and dilute with water to 35mL.The limit is 3ppm.

Lead— Using Ferrous Sulfate,proceed as directed in the test for Leadunder Ferrous Gluconate:the limit is 0.001%.

Mercury— It meets the requirements of the test for Mercuryunder Ferrous Fumarate.

Organic volatile impurities,Method IVá467ñ: meets the requirements.

Assay— Dissolve about 1g of 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 FeSO4or to 27.80mg of FeSO4·7H2O.

Expert Committee:(DSN)Dietary Supplements:Non-Botanicals

USP28–NF23Page 821

Phone Number:1-301-816-8389