Aluminum Chloride

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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AlCl₃ · 6H₂O 241.43

AlCl₃ 133.34

Aluminum chloride, hexahydrate;

Aluminum chloride hexahydrate CAS RN®: 7784-13-6; UNII: 3CYT62D3GA.

Anhydrous CAS RN®: 7446-70-0; UNII: LIF1N9568Y.

1 DEFINITION

Aluminum Chloride contains NLT 95.0% and NMT 102.0% of aluminum chloride (AlCl₃), calculated on the anhydrous basis.

2 IDENTIFICATION

A. Identification Tests—General, Aluminum〈191〉andChloride〈191〉

Sample solution: 100 mg/mL

Acceptance criteria: Meets the requirements

3 ASSAY

Procedure

Edetate disodium titrant: Prepare and standardize as directed in Reagents, Volumetric Solutions, Edetate Disodium, Twentieth-Molar (0.05 M). Sample solution: 20 mg/mL of aluminum chloride in water

Titrimetric system

Mode: Back-titration

Titrant: 0.05 M zinc sulfate VS

Endpoint detection: Visual

Analysis: Transfer 10.0 mL of the Sample 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, and boil gently for 5 min. Cool, and add 50 mL of alcohol and 2 mL of dithizone TS. Titrate the excess edetate disodium with Titrant to a bright rose-pink color. Perform a blank determination, substituting 10 mL of water for the Sample solution, and make any necessary correction. Each mL of Edetate disodium titrant consumed is equivalent to 6.667 mg of aluminum chloride (AlCl₃).

Acceptance criteria: 95.0%–102.0% on the anhydrous basis

4 IMPURITIES

4.1 Limit of Sulfate

Sample solution: 10 mg/mL

Analysis: Add 0.2 mL of barium chloride TS to 10 mL of the Sample solution.

Acceptance criteria: No turbidity is produced within 1 min.

4.2 Iron 〈241〉

Sample: 1.0 g

Analysis: Dissolve the Sample in 45 mL of water, and add 2 mL of hydrochloric acid.

Acceptance criteria: NMT 10 ppm

4.3 Limit of Alkalies and Alkaline Earths

Sample: 1.0 g

Analysis: To a boiling solution of the Sample in 150 mL of water add a few drops of methyl red TS, then add 6 N ammonium hydroxide until the color of the solution just changes to a distinct yellow. Add hot water to restore the volume to 150 mL, and lter while hot. Evaporate 75 mL of the filtrate to dryness, and ignite to a constant weight.

Acceptance criteria: 0.5%; the weight of the residue is NMT 2.5 mg.

5 SPECIFIC TESTS

Water Determination, Method I 〈921〉: 42.0%–48.0%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.