Packaging and storage—
Preserve in tight containers, and avoid freezing.
Identification—
A:
The addition of 3 N hydrochloric acid to a quantity of Oral Suspension, equivalent to about 500 mg of calcium carbonate, produces effervescence, and the resulting solution, after having been filtered, responds to the tests for
Calcium 
191
.
B:
Heat a quantity of Oral Suspension, equivalent to about 800 mg of magnesium carbonate, with 20 mL of 1 N sulfuric acid. Cool, add 20 mL of alcohol, mix, and allow to stand for 30 minutes. Filter this solution, and add 2 mL of 1 N hydrochloric acid to the filtrate: this solution responds to the tests for
Magnesium 191.
Microbial limits 61—
Its total aerobic microbial count does not exceed 100 cfu per mL, and it meets the requirements of the tests for absence of
Escherichia coli and
Pseudomonas aeruginosa.
Acid-neutralizing capacity 301—
Not less than 5 mEq of acid is consumed by the minimum single dose recommended in the labeling, and not less than the number of mEq calculated by the formula:
0.8(0.024M) + 0.9(0.02C),
in which 0.024 and 0.02 are the theoretical acid-neutralizing capacities, in mEq, of MgCO
3 and CaCO
3, respectively, and
M and
C are the respective quantities, in mg, of MgCO
3 and CaCO
3 in the specimen tested based on the labeled quantities.
Assay for calcium carbonate—
Transfer an accurately measured quantity of Oral Suspension, previously well shaken in its original container and free of air bubbles, equivalent to about 400 mg of calcium carbonate, to a beaker, with the aid of 20 mL of water, and add 10 mL of 1 N hydrochloric acid. Heat on a steam bath for 30 minutes, allow to cool, transfer with the aid of water to a 100-mL volumetric flask, dilute with water to volume, mix, and filter. Transfer 20.0 mL of the filtrate to a suitable container, dilute with water to 100 mL, add 15 mL of 1 N sodium hydroxide, 5 mL of triethanolamine, and 100 mg of hydroxynaphthol blue trituration, and titrate with 0.05 M edetate disodium VS until the solution is deep blue. Each mL of 0.05 M edetate disodium is equivalent to 5.004 mg of CaCO3.
Assay for magnesium carbonate—
Transfer an accurately measured portion of the filtrate remaining from the
Assay for calcium carbonate, equivalent to about 120 mg of calcium carbonate and magnesium carbonate combined, to a suitable container, dilute with water to 100 mL, add 10 mL of ammonia-ammonium chloride buffer TS, 5 mL of triethanolamine, and 0.3 mL of
eriochrome black TS, and titrate with 0.05
M edetate disodium VS to a blue endpoint. From the volume of 0.05
M edetate disodium consumed, subtract the volume of 0.05
M edetate disodium corresponding to the content of calcium carbonate in the volume of the filtrate taken for the
Assay for calcium carbonate. The difference is the volume of 0.05
M edetate disodium equivalent to the amount of magnesium carbonate present. Each mL of 0.05
M edetate disodium is equivalent to 4.216 mg of MgCO
3.
