Packaging and storage—
Preserve in tight, light-resistant containers, at controlled room temperature.
Identification—
Shake 1 mL with 10 mL of water containing 1 drop of 2 N sulfuric acid, and add 2 mL of ether: the subsequent addition of a drop of
potassium dichromate TS produces an evanescent blue color in the water layer which upon agitation and standing passes into the ether layer.
Acidity—
To 25 mL add phenolphthalein TS, and titrate with 0.10 N sodium hydroxide: not more than 2.5 mL is required for neutralization.
Barium—
To 10 mL add two drops of 2 N sulfuric acid: no turbidity or precipitate is produced within 10 minutes.
Heavy metals 
231
—
Dilute 4 mL, previously shaken, with 20 mL of water, add 2 mL of 6 N ammonium hydroxide, and gently boil the solution until the volume is reduced to about 5 mL. Dilute with water to 25 mL: the limit is 5 ppm.
Limit of nonvolatile residue—
Evaporate 20 mL, previously shaken, on a steam bath to dryness, and dry the residue at 105
for 1 hour: the weight of the residue does not exceed 30 mg.
Limit of preservative—
Extract 100 mL of well-mixed Topical Solution in a separator with a mixture of 3 volumes of chloroform and 2 volumes of ether, using 50 mL, 25 mL, and 25 mL, respectively. Evaporate the combined extracts at room temperature in a tared glass dish to dryness, and dry over silica gel for 2 hours: the residue, if any, weighs not more than 50 mg (0.05%).
Assay—
Pipet 2 mL of Topical Solution into a suitable flask containing 20 mL of water. Add 20 mL of 2 N sulfuric acid, and titrate with 0.1 N potassium permanganate VS. Each mL of 0.1 N potassium permanganate is equivalent to 1.701 mg of H2O2.
