Na2CO3 (anhydrous) 105.99

Carbonic acid, disodium salt.
Disodium carbonate [497-19-8].

Monohydrate 124.00 [5968-11-6].

Packaging and storage— Preserve in well-closed containers.

Labeling— Label it to indicate whether it is anhydrous or hydrous.

Identification— It responds to the tests for Sodium 191 and for Carbonate 191.

Water, Method III 921— Dry about 2 g, accurately weighed, at 105 for 4 hours: the anhydrous form loses not more than 0.5%, and the hydrous form between 12.0% and 15.0%, of its weight.

Heavy metals 231— Dissolve 2.0 g in 10 mL of water, add 1 drop of phenolphthalein TS, and neutralize the solution with hydrochloric acid, added dropwise. Heat the solution to boiling, and again neutralize by the dropwise addition of hydrochloric acid. Cool, and dilute with water to 25 mL: the limit is 0.001%.

Assay— Transfer the anhydrous sodium carbonate obtained in the test for Water to a flask with the aid of 50 mL of water, add methyl red TS, and titrate with 1 N sulfuric acid VS. Add the acid slowly, with constant stirring, until the solution becomes faintly pink. Heat the solution to boiling, cool, and continue the titration. Heat again to boiling, and titrate further as necessary until the faint pink color is no longer affected by continued boiling. Each mL of 1 N sulfuric acid is equivalent to 52.99 mg of Na2CO3.

Topic/Question	Contact	Expert Committee
Monograph	Robert H. Lafaver, B.A. Scientist 1-301-816-8335	(EM105) Excipient Monographs 1

USP32–NF27 Page 1341

SODIUM CARBONATE

Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.