Potassium Carbonate
(poe tas' ee um kar' bo nate).

K2CO3 (anhydrous) 138.21
K2CO3·1½H2O 165.23
Carbonic acid, dipotassium salt;    
Dipotassium carbonate     [584-08-7].
Potassium Carbonate contains NLT 99.5% and NMT 100.5% of K2CO3, calculated on the dried basis.
•  A. Identification Tests—General, Potassium 191: Meets the requirements
•  B. Identification Tests—General, Carbonate 191: Meets the requirements
•  Procedure
Sample:  Dried potassium carbonate obtained in the test for Loss on Drying
Analysis:  Transfer the Sample to a flask with the aid of 150 mL of water, and add 4 drops of methyl orange TS. Titrate with 1 N hydrochloric acid VS. Each mL of 1 N hydrochloric acid is equivalent to 69.11 mg of K2CO3.
Acceptance criteria:  99.5%–100.5% on the dried basis
•  Heavy Metals 231
Analysis:  Dissolve 4.0 g in 10 mL of water. Add 15 mL of 3 N hydrochloric acid, and heat to boiling. Add 1 drop of phenolphthalein TS, and neutralize with 1 N sodium hydroxide until the solution is faintly pink in color. Cool, and dilute with water to 25 mL.
Acceptance criteria:  NMT 5 ppm
•  Loss on Drying 731: Dry a sample at 180 for 4 h: it loses NMT 0.5% of its weight.
•  Insoluble Substances
Sample solution:  1 g in 20 mL of water
Acceptance criteria:  The solution is complete, clear, and colorless.
•  Packaging and Storage: Preserve in well-closed containers.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Sujatha Ramakrishna, Ph.D.
Senior Scientific Liaison
(SM22010) Monographs - Small Molecules 2
USP35–NF30 Page 4359