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

KHCO3 100.12
Carbonic acid, monopotassium salt;    
Monopotassium carbonate     [298-14-6].
DEFINITION
Potassium Bicarbonate contains NLT 99.5% and NMT 101.5% of KHCO3, calculated on the dried basis.
IDENTIFICATION
•  A. Identification Tests—General, Potassium 191
Sample solution:  100 mg/mL
Acceptance criteria:  Meets the requirements
•  B. Identification Tests—General, Bicarbonate 191
Sample solution:  100 mg/mL
Acceptance criteria:  Meets the requirements
ASSAY
•  Procedure
Sample:  4 g
Analysis:  Dissolve the Sample in 100 mL of water, add methyl red TS, and titrate with 1 N hydrochloric 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 until the pink color no longer fades after boiling. Each mL of 1 N hydrochloric acid is equivalent to 100.1 mg of KHCO3.
Acceptance criteria:  99.5%–101.5% on the dried basis
IMPURITIES
•  Heavy Metals, Method I 231
Sample solution:  To 2 g add 5 mL of water and 8 mL of 3 N hydrochloric acid, heat to boiling, and maintain that temperature for 1 min. Add 1 drop of phenolphthalein TS and sufficient 6 N ammonium hydroxide, dropwise, to give the solution a faint pink color. Cool, add 2 mL of 1 N acetic acid, and then dilute with water to 25 mL.
Acceptance criteria:  NMT 10 ppm
SPECIFIC TESTS
•  Loss on Drying 731: Dry a sample over silica gel for 4 h: it loses NMT 0.3% of its weight.
•  Normal Carbonate
Sample:  Grind 3.0 g of Potassium Bicarbonate with 25 mL of alcohol and 5 mL of water in a porcelain mortar.
Barium chloride solution:  12.216 mg/mL of barium chloride in alcohol and water (7:3), prepared by dissolving the barium chloride in water, then diluting with alcohol to final volume
Analysis:  Add 3 drops of phenolphthalein TS to the Sample, and titrate slowly with Barium chloride solution until the suspension becomes colorless. Continue the grinding for 2 min, and if the color turns pink, continue the titration with Barium chloride solution to a colorless endpoint. Repeat the grinding for 2 min and the addition of Barium chloride solution, if necessary, until the suspension is colorless after 2 min of grinding. Each mL of the barium chloride solution is equivalent to 6.911 mg of K2CO3.
Acceptance criteria:  NMT 2.5%
ADDITIONAL REQUIREMENTS
•  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 Mary S. Waddell
Scientific Liaison
1-301-816-8124
(SM42010) Monographs - Small Molecules 4
USP35–NF30 Page 4354