Sodium Carbonate
Na2CO3 (anhydrous) 105.99
Na2CO3·H2O 124.00
Carbonic acid, disodium salt;
Disodium carbonate
[497-19-8].
Monohydrate[5968-11-6].
(soe' dee um kar' bo nate).
Na2CO3 (anhydrous) 105.99
Na2CO3·H2O 124.00
Carbonic acid, disodium salt;
Disodium carbonate
[497-19-8].Monohydrate
[5968-11-6].DEFINITION
Sodium Carbonate is anhydrous or contains one molecule of water of hydration. It contains NLT 99.5% and NMT 100.5% of Na2CO3, calculated on the anhydrous basis.
IDENTIFICATION
• A. Identification Tests—General, Sodium 
191
:
Meets the requirements
191:
Meets the requirements
• B. Identification Tests—General, Carbonate 191:
Meets the requirements
191:
Meets the requirements
ASSAY
• Procedure
Sample:
2 g of Sodium Carbonate, previously dried, from the test for Water Determination
Blank:
50 mL of water
Titrimetric system
(See Titrimetry 541.)
541.)
Mode:
Direct titration
Titrant:
1 N sulfuric acid VS
Endpoint detection:
Visual
Analysis:
Transfer the Sample 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.
Calculate the percentage of sodium carbonate (Na2CO3) in the Sample taken.
Result = [(V 
B) × N × F × 100]/W
B) × N × F × 100]/W
| V | = | = Titrant volume consumed by the Sample (mL) |
| B | = | = Titrant volume consumed by the Blank (mL) |
| N | = | = Titrant actual normality (mEq/mL) |
| F | = | = equivalency factor, 52.99 mg/mEq |
| W | = | = weight of the Sample (mg) |
Acceptance criteria:
99.5%–100.5% on the anhydrous basis
IMPURITIES
• Heavy Metals 231
231
Test preparation:
Dissolve 2.0 g in 10 mL of water.
Analysis:
Add 1 drop of phenolphthalein TS to the Test preparation, 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. Proceed as directed in the chapter.
Acceptance criteria:
NMT 10 ppm
SPECIFIC TESTS
• Water Determination, Method III 921
921
Sample:
2 g
Analysis:
Dry the Sample at 105
for 4 h.
for 4 h.
Acceptance criteria:
The anhydrous form loses NMT 0.5% of its weight, and the hydrous form loses 12.0%–15.0% of its weight.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
• Labeling:
Label it to indicate whether it is anhydrous or hydrous.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Robert H. Lafaver, M.S.
Scientific Liaison 1-301-816-8335 |
(EXC2010) Monographs - Excipients |
USP35–NF30 Page 1952