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 á191ñand for Carbonate á191ñ.

Water,Method IIIá921ñ— Dry about 2g,accurately weighed,at 105for 4hours:the anhydrous form loses not more than 0.5%,and the hydrous form between 12.0%and 15.0%,of its weight.

Heavy metals á231ñ— Dissolve 2.0g in 10mLof water,add 1drop 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 25mL:the limit is 0.001%.

Organic volatile impurities,Method Iá467ñ: meets the requirements.

Assay— Transfer the anhydrous sodium carbonate obtained in the test for Waterto a flask with the aid of 50mLof water,add methyl red TS,and titrate with 1Nsulfuric 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 mLof 1Nsulfuric acid is equivalent to 52.99mg of Na2CO3.

Expert Committee:(EMC)Excipients:Monograph Content

USP28–NF23Page 3075

Phone Number:1-301-816-8262