(a loo' mi num sul' fate).
Al2(SO4)3·xH2O (anhydrous) 342.15
Sulfuric acid, aluminum salt (3:2), hydrate.
Aluminum sulfate (2:3) hydrate [17927-65-0].
Anhydrous 342.16 [10043-01-3].
» Aluminum Sulfate contains not less than 54.0 percent and not more than 59.0 percent of Al2(SO4)3. It contains a varying amount of water of crystallization.
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).
Water, Method I 921: not less than 41.0% and not more than 46.0%.
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.
Iron To 20 mL of a solution (1 in 150) add 0.3 mL of potassium ferrocyanide TS: no blue color is produced immediately.
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 Al2(SO4)3.