Aluminum Subacetate Topical Solution
» Aluminum Subacetate Topical Solution yields, from each 100 mL, not less than 2.30 g and not more than 2.60 g of aluminum oxide (Al2O3), and not less than 5.43 g and not more than 6.13 g of acetic acid (C2H4O2). It may be stabilized by the addition of not more than 0.9 percent of boric acid.
Aluminum Subacetate Topical Solution may be prepared as follows.
Dissolve the Aluminum Sulfate in 600 mL of cold water, filter the solution, and add the Calcium Carbonate gradually, in several portions, with constant stirring. Then slowly add the Acetic Acid, mix, and set the mixture aside for 24 hours. Filter the product with the aid of vacuum if necessary, returning the first portion of the filtrate to the funnel. Wash the magma on the filter with small portions of cold water, until the total filtrate measures 1000 mL.
Packaging and storage Preserve in tight containers.
Identification It responds to the tests for Aluminum 191 and for the ferric chloride test for Acetate 191 with a deep red color upon the addition of ferric chloride TS. This color is destroyed by the addition of a mineral acid.
pH 791: between 3.8 and 4.6.
Limit of boric acid Proceed as directed in the test for Limit of boric acid under Aluminum Acetate Topical Solution.
Assay for aluminum oxide
Procedure Pipet 20 mL of Topical Solution into a 250-mL volumetric flask, add 5 mL of hydrochloric acid, dilute with water to volume, and mix. Pipet 25 mL of this dilution into a 250-mL beaker, and proceed as directed for Procedure 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 2.549 mg of Al2O3.
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USP35NF30 Page 2136Pharmacopeial Forum: Volume No. 34(2) Page 242