Packaging and storage—
Preserve in tight containers.
Completeness and color of solution—
It is completely soluble in its own weight of cold water, the solution being colorless or not more than slightly yellow when viewed transversely in a tube having a diameter of about 20 mm.
Identification—
B:
Ultraviolet Absorption 
197U
—
Solution:
20 µg per mL.
Medium:
methanol.
Absorptivities at 266 nm, calculated on the dried basis, do not differ by more than 3.0%.
C:
Add
tannic acid TS to a solution of it: a white precipitate is formed.
Heavy metals 231—
Dissolve 1 g in 2 mL of 1 N acetic acid, and add water to make 25 mL: the limit is 0.002%.
Ordinary impurities 466—
Test solution:
chloroform.
Standard solution:
chloroform.
Eluant:
a mixture of chloroform, acetone, butyl alcohol, and formic acid (60:15:15:15).
Visualization:
1.
Assay—
Transfer about 150 mg of Antipyrine, accurately weighed, to a 250-mL iodine flask, and dissolve in 25 mL of water. Add 2 g of sodium acetate, 1 mL of diluted acetic acid, and 20.0 mL of 0.1 N iodine VS, mix, and allow to stand in a cool, dark place for 20 minutes. Add 25 mL of alcohol to dissolve the precipitate, and titrate the excess iodine with 0.1 N sodium thiosulfate VS, using
starch TS as the indicator. Each mL of 0.1 N iodine is equivalent to 9.412 mg of C
11H
12N
2O.
;)
for 2 hours: it loses not more than 1.0% of its weight.