Aluminum Hydroxide Gel
Aluminum hydroxide [21645-51-2].
» Aluminum Hydroxide Gel is a suspension of amorphous aluminum hydroxide in which there is a partial substitution of carbonate for hydroxide. It contains the equivalent of not less than 90.0 percent and not more than 110.0 percent of the labeled amount of aluminum hydroxide [Al(OH)3]. It may contain Peppermint Oil, Glycerin, Sorbitol, Sucrose, Saccharin, or other suitable flavors, and it may contain suitable antimicrobial agents.
Packaging and storage Preserve in tight containers, and avoid freezing.
A: Place about 1 g in a flask equipped with a stopper and glass tubing, the tip of which is immersed in calcium hydroxide TS in a test tube. Add 5 mL of 3 N hydrochloric acid to the flask, and immediately insert the stopper: gas evolves in the flask and a precipitate is formed in the test tube.
B: The solution remaining in the flask responds to the tests for Aluminum 191.
Microbial enumeration tests 61 and Tests for specified microorganisms 62 Its total aerobic microbial count does not exceed 100 cfu per mL, and it meets the requirements of the test for the absence of Escherichia coli.
Acid-neutralizing capacity 301 Not less than 65.0% of the expected mEq value, calculated from the results of the Assay, is obtained. Each mg of Al(OH)3 has an expected acid-neutralizing capacity value of 0.0385 mEq.
pH 791: between 5.5 and 8.0, determined potentiometrically.
Chloride Transfer an accurately measured quantity of the Gel, equivalent to 0.6 g of Al(OH)3, to a porcelain dish. Add 0.1 mL of potassium chromate TS and 25 mL of water. Stir, and add 0.10 N silver nitrate until a faint, persistent pink color is obtained: not more than 8.0 mL of 0.10 N silver nitrate is required [4.7%, based on the Al(OH)3 content].
Sulfate 221 Add 5.0 mL of 3 N hydrochloric acid to an accurately measured quantity of the Gel, equivalent to 0.3 g of Al(OH)3, and heat to dissolve the specimen under test. Cool, dilute with water to 250 mL, and filter if necessary: a 20-mL portion of the filtrate shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid [0.8%, based on the Al(OH)3 content].
Arsenic, Method I 211 Prepare a Standard Preparation as directed in the test for Arsenic 211, except to prepare it to contain 5 µg of arsenic instead of 3 µg. Prepare the Test Preparation as follows. Dissolve an accurately measured quantity of the Gel, equivalent to 0.5 g of Al(OH)3, in 20 mL of 7 N sulfuric acid. The limit is 0.001%, based on the Al(OH)3 content.
Heavy metals 231 Dissolve an accurately measured quantity of the Gel, equivalent to 0.24 g of Al(OH)3, in 10 mL of 3 N hydrochloric acid with the aid of heat, filter, if necessary, and dilute with water to 25 mL: the limit is 0.0083%, based on the Al(OH)3 content.
Procedure Transfer an accurately measured quantity of Gel, equivalent to about 1.5 g of Al(OH)3, to a beaker, add 15 mL of hydrochloric acid, and heat gently until solution is complete. Cool, transfer to a 500-mL volumetric flask, dilute with water to volume, and mix. Pipet 20 mL of this solution into a 250-mL beaker, and add, in the order named and with continuous stirring, 25.0 mL of Edetate disodium titrant and 20 mL of acetic acidammonium acetate buffer TS, then heat the solution near the boiling point for 5 minutes. Cool, and add 50 mL of alcohol and 2 mL of dithizone TS. Titrate the solution with 0.05 M zinc sulfate VS until the color changes from green-violet to rose-pink. Perform a blank determination, substituting 20 mL of water for the sample, and make any necessary correction. Each mL of 0.05 M Edetate disodium titrant consumed is equivalent to 3.900 mg of Al(OH)3.
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USP35NF30 Page 2131