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Sodium Carbonate
Soda Ash
Na2CO3 Formula wt, anhydrous 105.99
Na2CO3•H2O Formula wt, monohydrate 124.00
Na2CO3•10H2O Formula wt, decahydrate 286.14
INS: 500(i) CAS: anhydrous [497-19-8]
CAS: monohydrate [5968-11-6]
CAS: decahydrate [6132-02-1]
DESCRIPTION
Sodium Carbonate occurs as colorless crystals or as a white,
granular or crystalline powder. It is anhydrous or may contain
1 or 10 molecules of water of hydration. It is freely soluble
in water and insoluble in ethanol. Its solutions are alkaline
to litmus. The anhydrous salt is hygroscopic, and the two
hydrates are efflorescent. The decahydrate melts at about 32°.
Function pH control.
REQUIREMENTS
Identification A sample gives positive tests for Sodium and
for Carbonate, Appendix IIIA.
Assay Not less than 99.5% and not more than 100.5% of
Na2CO3 after drying.
Lead Not more than 4 mg/kg.
Loss on Drying Anhydrous: Not more than 1%; Monohy-
drate: Between 12.0% and 15.0%; Decahydrate: Between
55.0% and 65.0%.
TESTS
Assay Accurately weigh about 2 g of the dried sample,
obtained as directed under Loss on Drying (below), and dis-
solve it in 50 mL of water. Add 2 drops of methyl red TS,
and titrate with 1 N hydrochloric acid, adding the acid slowly,
while constantly stirring, until the solution becomes faintly
pink. Heat the solution to boiling, cool, and continue the
titration until the faint pink color no longer fades after boiling.
Each milliliter of 1 N hydrochloric acid is equivalent to 53.00
mg of Na2CO3.
Lead Determine as directed in the APDC ExtractionMethod
under Lead Limit Test, Appendix IIIB.
Loss on Drying Determine as directed under Loss on Dry-
ing, Appendix IIC, drying about 3 g of the anhydrous or
monohydrate sample, accurately weighed, at 275° to 300° to
constantweight. For the decahydrate, heat about 8 g of sample,
accurately weighed, first at 70°, then gradually raise the tem-
perature, and dry the sample at 275° to 300° to constant
weight.
Tiêu chuẩn natri cacbonat
Linear Mode
