Packaging and storage—
Preserve in well-closed containers.
Identification—
A solution (1 in 10) responds to the tests for
Aluminum and for
Sulfate 
191
.
pH 791:
not less than 2.9, in a solution (1 in 20).
Heavy metals 231—
Dissolve 1.0 g in 2 mL of 1 N acetic acid, and dilute with water to 25 mL. The limit is 20 µg per g.
Limit of alkalies and alkaline earths—
To a boiling solution of 1.0 g in 150 mL of water add a few drops of
methyl red TS and then add 6 N ammonium hydroxide just until the color of the solution changes to a distinct yellow. Add hot water to restore the volume to 150 mL, and filter while hot. Evaporate 75 mL of the filtrate to dryness, and ignite to constant weight: not more than 2 mg of residue remains (0.4%).
Limit of ammonium salts—
Heat 1 g with 10 mL of 1 N sodium hydroxide on a steam bath for 1 minute: the odor of ammonia is not perceptible.
Organic volatile impurities, Method IV 467:
meets the requirements.
Assay—
Edetate disodium titrant—
Prepare and standardize as directed in the
Assay under
Ammonium Alum.
Procedure—
Transfer about 7.5 g of Aluminum Sulfate, accurately weighed, to a 250-mL volumetric flask, and dissolve in water. Dilute with water to volume, mix, and pipet 10 mL of the solution into a 250-mL beaker. Proceed as directed in the
Assay for aluminum oxide under
Aluminum Acetate Topical Solution, beginning with “add, in the order named.” Each mL of 0.05 M
Edetate disodium titrant is equivalent to 8.554 mg of Al
2(SO
4)
3.
