A: Place approximately 0.25 g of Aluminum Sulfate and Calcium Acetate for Topical Solution in a test tube. Add 10 mL of water and 0.25 g of calcium carbonate. Heat on a steam bath for 10 minutes, and filter. Add 3 to 4 drops of ferric chloride TS to the filtrate. A reddish-brown color or precipitate indicates acetate. [note—After the addition of the ferric chloride TS, the solution may be heated for 1 minute to speed the reaction.]

B: Suspend 2 g of sample in 50 mL of water, and filter. The filtrate meets the requirements of the tests for Sulfate 191 and for Calcium 191.

Assay preparation— Transfer 10 g of Aluminum Sulfate and Calcium Acetate for Topical Solution, accurately weighed, to a 1000-mL volumetric flask. Add 100 mL of 1.2 M hydrochloric acid and approximately 250 mL of water. Heat on a steam bath or hot plate until dissolved. Cool, dilute with water to volume, and mix. [note—Retain a portion of this Assay preparation for the Assay for calcium acetate.]

Procedure— Transfer a 5.0-mL aliquot of the Assay preparation to a 250-mL conical flask. Add 40.0 mL of 0.01 M edetate disodium VS and 20 mL of acetic acid–ammonium acetate buffer TS, and mix well. Add 50 mL of alcohol and 2 mL of dithizone TS. [note—Follow the given order of addition.] Titrate with 0.02 M zinc sulfate VS until the color changes from green-violet to clear rose-pink. Perform a blank titration, substituting 5.0 mL of water for the Assay preparation. Each mL of 0.01 M edetate disodium is equivalent to 2.972 mg of aluminum sulfate tetradecahydrate [Al2(SO4)3·14H2O]. Calculate the percentage of aluminum sulfate tetradecahydrate [Al2(SO4)3·14H2O] by the formula: in which 1000/5.0 is the dilution factor; 100 is the conversion factor to percentage; CF is the conversion factor (2.972 mg of sample per mL of 0.01 M edetate disodium); M is the actual molarity of the titrant; VB is the blank titration volume, in mL; VU is the sample titration volume, in mL; MT is the theoretical molarity of the titrant (0.02); and W is the weight of the sample, in mg.

Procedure— Transfer a 5.0-mL aliquot of the Assay preparation retained from the Assay for aluminum sulfate to a 250-mL conical flask. Add 1 to 2 mL of 50% triethanolamine to mask the aluminum. Mix well. Add 100 mL of water, 15 mL of 1 N sodium hydroxide, and approximately 300 mg of hydroxy naphthol blue. [note—Follow the given order of addition.] Titrate the solution with 0.01 M edetate disodium VS. The indicator will change from purple to a clear blue color at the endpoint. Each mL of 0.01 M edetate disodium is equivalent to 1.762 mg of calcium acetate monohydrate (C4H6CaO4·H2O). Calculate the percentage of calcium acetate monohydrate (C4H6CaO4·H2O) by the formula: in which 1000/5.0 is the dilution factor; 100 is the conversion factor to percentage; VU is the sample titration volume, in mL; CF is the conversion factor (1.762 mg of sample per mL of 0.01 M edetate disodium); M is the actual molarity of the titrant; MT is the theoretical molarity of the titrant (0.01); and W is the weight of the sample, in mg.