Packaging and storage—
Preserve in well-closed containers.
Dissolution 
711
—
Medium:
0.1 N hydrochloric acid; 900 mL.
Apparatus 2:
75 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of MgO dissolved, employing atomic absorption spectrophotometry at a wavelength of about 285.2 nm using filtered portions of the solution under test, suitably diluted with Medium if necessary, in comparison with a standard solution having a known concentration of magnesium in the same Medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of MgO is dissolved in 45 minutes.
Acid-neutralizing capacity 301 (where Tablets are labeled as intended for antacid use):
not less than 5 mEq of acid is consumed by the minimum single dose recommended in the labeling, and not less than 85.0% of the expected mEq value calculated from the results of the
Assay is obtained. Each mg of MgO has an expected acid-neutralizing capacity value of 0.0492 mEq.
Assay—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 500 mg of magnesium oxide, to a beaker. Proceed as directed in the
Assay under
Magnesium Oxide Capsules beginning with “add 20 mL of water.” Each mL of 0.05
M edetate disodium consumed is equivalent to 2.015 of mg of magnesium oxide (MgO).
