Packaging and storage—
Preserve in tight containers, protected from light, and avoid prolonged exposure to temperatures exceeding 30
.
Identification—
Transfer an amount of Topical Solution, equivalent to about 5 mg of benzocaine, to a small beaker, add 20 mL of 0.5 N hydrochloric acid, warm gently to disperse, cool, and filter. To 10 mL of the filtrate add 5 drops of sodium nitrite solution (1 in 10) and 2 drops of
methyl red TS, and neutralize with 1 N sodium hydroxide. Add 2 mL of a solution of 100 mg of 2-naphthol in 5 mL of 1 N sodium hydroxide: an orange-red precipitate is formed.
Microbial limits 
61
—
It meets the requirements of the tests for absence of
Staphylococcus aureus and
Pseudomonas aeruginosa.
Assay—
Transfer an accurately weighed portion of Topical Solution, equivalent to about 200 mg of benzocaine, to a 250-mL beaker. Add 50 mL of water and 5 mL of hydrochloric acid, and stir. Cool the solution in an ice bath to about 10
, and titrate slowly with 0.1
M sodium nitrite VS, determining the endpoint potentiometrically, using a calomel-platinum electrode system. Perform a blank determination, and make any necessary correction. Each mL of 0.1
M sodium nitrite is equivalent to 16.52 mg of C
9H
11NO
2.
