Dried Aluminum Hydroxide Gel
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
Aluminum hydroxide CAS RN®: 21645-51-2; UNII: 5QBOT2IUNO.
» Dried Aluminum Hydroxide Gel is an amorphous form of aluminum hydroxide in which there is a partial substitution of carbonate for hydroxide. It contains the equivalent of not less than 76.5 percent of Al(OH)3, and it may contain varying quantities of basic aluminum carbonate and bicarbonate.
Packaging and storage—Preserve in tight containers.
Labeling—Where the quantity of dried aluminum hydroxide gel equivalent is stated in the labeling of any preparation, this shall be understood to be on the basis that each mg of dried gel is equivalent to 0.765 mg of Al(OH)3
Identification—
A: Spectroscopic Identification Tests (197), Infrared Spectroscopy: 197K
B: Dissolve 500 mg in 10 ml of 3 N hydrochloric acid, with gentle warning: the solution responds to the tests for Aluminum (191)
ACID-NEUTRALIZING CAPACITY (301): not less than 25.0 mEq per g. 400 mg being tested as directed for Powders under Test Preparation.
H.(791): not higher than 10.0, in an aqueous dispersion (1 in 25).
CHLORIDE (221) Dissolve 1.0 g in 30 mL of 2 N nitric acid, heat to boiling, add water to make 100 mL, and filter: a 5.0-ml portion of the filtrate, diluted with an equal volume of water, shows no more chloride than corresponds to 0.60 mL of 0.020 N hydrochloric acid (0.85%).
SIAFATE (221)-Dissolve 330 mg in 15 ml of 3 N hydrochloric acid, heat to boiling, add water to make 250 ml, and filter. a 25-ml. portion of the filtrate shows no more sulfate than corresponds to 0.20 mL of 0.020 N sulfuric acid (0.6%).
Change to read:
ARSENIC (211), Procedures. Procedure 1 (CN 1-Jun-2023) -Dissolve 1.5 g in 80 mL of 7 N sulfuric acid, and dilute with water to 220 mL: 55 ml of the resulting solution meets the requirements of the test, the addition of 20 mL of 7 N sulfuric acid specified under Procedure being omitted. The limit is 8 ppm.
Assay—
Edetate disodium titrant-Prepare and standardize as directed in the Assay under Ammonium Alum
Procedure-Weigh accurately about 2 g of Gel, and dissolve in 15 ml. of hydrochloric acid, with the aid of heat. 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 acid-ammonium 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 to a bright rose-pink color. Perform a blank determination, substituting 20 ml of water for the sample solution, and make any necessary correction. Each ml. of 0.05 M Edetate disodium titrant is equivalent to 3.900 mg of Al(OH)3.
