Packaging and storage—
Preserve in tight containers, and avoid excessive heat.
Identification—
A:
Suspend 2 g of ground Tablet powder in 50 mL of water, and filter. Mix 2 mL of the filtrate with 2 mL of water and 2 drops of 3 N hydrochloric acid: the solution responds to the ammonium hydroxide test for
Aluminum 
191
.
[NOTE—Retain the remaining filtrate for
Identification test
B.
]
B:
A portion of the filtrate retained from
Identification test
A responds to the tests for
Sulfate 191 and for
Calcium 191.
pH 791:
between 4.0 and 4.8, in a solution (2 g of ground Tablet powder in 500 mL of water).
Loss on drying 731—
Dry ground Tablet powder at 150
for 15 minutes: it loses not more than 18% of its weight.
Assay for aluminum sulfate—
Assay preparation—
Finely powder and mix not fewer than 20 Tablets. Weigh accurately a portion of the powder, equivalent to about 2.8 g of aluminum sulfate, and transfer to a 1000-mL volumetric flask. Add 100 mL of 1.2 N hydrochloric acid and 100 mL of water, and heat on a steam bath, with occasional swirling, to dissolve the powder. Allow the solution to cool, dilute with water to volume, and mix. [NOTE—Retain a portion of this Assay preparation for the Assay for calcium acetate.]
Procedure—
Transfer 25.0 mL of the
Assay preparation to a 250-mL conical flask. Add 40.0 mL of 0.01
M edetate disodium VS and 20 mL of acetic acid–ammonium acetate buffer TS, and mix by swirling. Add 50 mL of alcohol and 2 mL of
dithizone TS, and titrate with 0.02
M zinc sulfate VS until the color changes from green-violet to a clear rose-pink. Perform a blank determination, substituting 25 mL of water for the
Assay preparation, and make any necessary correction. Each mL of 0.01
M edetate disodium is equivalent to 2.972 mg of Al
2(SO
4)
3·14H
2O.
Assay for calcium acetate—
Transfer 20.0 mL of the
Assay preparation retained from the
Assay for aluminum sulfate to a 125-mL conical flask. With constant stirring, add in the order named, about 0.5 mL of trolamine, 10 mL of ammonia–ammonium chloride buffer TS, and 3 drops of a solution prepared by dissolving 500 mg of eriochrome black T trituration in 10 mL of methanol, and titrate with 0.01
M edetate disodium VS to a violet endpoint. Each mL of 0.01
M edetate disodium is equivalent to 1.762 mg of C
4H
6CaO
4·H
2O.
