Molecular formula. NaHCO₃

Relative molecular mass. 84.01

Chemical name. Monosodium carbonate; CAS Reg. No. 144-55-8.

Other name. Sodium bicarbonate.

Description. A white, crystalline powder; odourless.

Solubility. Soluble in water; practically insoluble in ethanol (~750 g/l) TS.

Category. Systemic alkalinizing agent; antacid.

Storage. Sodium hydrogen carbonate should be kept in well-closed containers.

Additional information. Sodium hydrogen carbonate has a saline and slightly alkaline taste. It is stable in air, but slowly decomposes in moist air.

Requirements

Definition. Sodium hydrogen carbonate contains not less than 99.0% and not more than 101.0% of NaHCO₃, calculated with reference to the dried substance.

Identity tests

A. When tested for sodium as described under 2.1 General identification tests, yields the characteristic reactions. If reaction B is to be used, prepare a 20 mg/mL solution.

B. To a small amount add hydrochloric acid (~70 g/l) TS; it effervesces and the gas is colourless. Add a few drops of calcium hydroxide TS; immediately a white precipitate is formed.

C. To a 20 mg/mL solution add at room temperature a few drops of magnesium sulfate (50 g/l) TS; no precipitate is formed. Boil the mixture; a white precipitate is formed.

Heavy metals. Use 1.0 g for the preparation of the test solution as described under 2.2.3 Limit test for heavy metals. Procedure 1; determine the heavy metals content according to Method A; not more than 10 μg/g.

Ammonium. Heat 1.0 g in a test-tube; the gas evolved does not turn moistened red litmus paper R blue.

Arsenic. Use a solution of 3.3 g in 35 mL of water and proceed as described under 2.2.5 Limit test for arsenic; the arsenic content is not more than 3 μg/g.

Calcium. Boil a 20 mg/mL solution for 5 minutes; the solution is clear or at most very slightly opalescent.

Carbonates. pH of a 50 mg/mL solution in carbon-dioxide-free water R, not more than 8.6.

Chlorides. Dissolve 1.7 g in a mixture of 2 mL of nitric acid (~130 g/l) TS and 40 mL of water, and proceed as described under 2.2.1 Limit test for chlorides; the chloride content is not more than 0.15 mg/g.

Sulfates. Dissolve 2.5 g in 40 mL of water, add 1 mL of hydrochloric acid (~250 g/l) TS, and proceed as described under 2.2.2 Limit test for sulfates; the sulfate content is not more than 0.2 mg/g.

Clarity and colour of solution. A solution of 0.50 g in 10 mL of carbon-dioxide-free water R is clear and colourless.

Loss on drying. Dry to constant weight over silica gel, desiccant, R at ambient temperature; it loses not more than 2.5 mg/g.

Assay. Dissolve about 0.5 g, accurately weighed, in 50 mL of water and titrate with hydrochloric acid (0.2 mol/l) VS, using 3 drops of methyl orange/ethanol TS as indicator. Each mL of hydrochloric acid (0.2 mol/l) VS is equivalent to 16.80 mg of NaHCO₃.

Additional requirements for sodium hydrogen carbonate for parenteral use

Complies with the monograph for "Parenteral preparations".

Bacterial endotoxins. Carry out the test as described under 3.4 Test for bacterial endotoxins; contains not more than 5.0IU of endotoxin RS per milliequivalence.