Dried Aluminum Hydroxide Gel
Al(OH)3 78.00

Aluminum hydroxide [21645-51-2].
»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 76.5percent 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 0.765mg of Al(OH)3.
Identification—
A: Infrared Absorption á197Kñ.
B: Dissolve 500mg in 10mLof 3Nhydrochloric acid,with gentle warming:the solution responds to the tests for Aluminum á191ñ.
Acid-neutralizing capacity á301ñ: not less than 25.0mEq per g,400mg being tested as directed for Powdersunder Test Preparation.
pHá791ñ: not higher than 10.0,in an aqueous dispersion (1in 25).
Chloride á221ñ— Dissolve 1.0g in 30mLof 2Nnitric acid,heat to boiling,add water to make 100mL,and filter:a 5.0-mLportion of the filtrate,diluted with an equal volume of water,shows no more chloride than corresponds to 0.60mLof 0.020Nhydrochloric acid (0.85%).
Sulfate á221ñ— Dissolve 330mg in 15mLof 3Nhydrochloric acid,heat to boiling,add water to make 250mL,and filter:a 25-mLportion of the filtrate shows no more sulfate than corresponds to 0.20mLof 0.020Nsulfuric acid (0.6%).
Arsenic,Method Iá211ñ— Dissolve 1.5g in 80mLof 7Nsulfuric acid,and dilute with water to 220mL:55mLof the resulting solution meets the requirements of the test,the addition of 20mLof 7Nsulfuric acid specified under Procedurebeing omitted.The limit is 8ppm.
Heavy metals á231ñ— Dissolve 330mg in 10mLof 3Nhydrochloric acid with the aid of heat,filter if necessary,and dilute with water to 25mL:the limit is 0.006%.
Assay—
Edetate disodium titrant— Prepare and standardize as directed in the Assayunder Ammonium Alum.
Procedure— Weigh accurately about 2g of Gel,and dissolve in 15mLof hydrochloric acid,with the aid of heat.Cool,transfer to a 500-mLvolumetric flask,dilute with water to volume,and mix.Pipet 20mLof this solution into a 250-mLbeaker,and add,in the order named and with continuous stirring,25.0mLof Edetate disodium titrantand 20mLof acetic acid–ammonium acetate buffer TS,then heat the solution near the boiling point for 5minutes.Cool,and add 50mLof alcohol and 2mLof dithizone TS.Titrate the solution with 0.05Mzinc sulfate VSto a bright rose-pink color.Perform a blank determination,substituting 20mLof water for the sample solution,and make any necessary correction.Each mLof 0.05MEdetate disodium titrantis equivalent to 3.900mg of Al(OH)3.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 93
Phone Number:1-301-816-8251