Packaging and storage—
Preserve in tight, light-resistant containers.
Identification—
Transfer a volume of Otic Solution, equivalent to about 2.5 mg of benzocaine, to a small beaker, add 10 mL of water, and dissolve with the aid of a few drops of 3 N hydrochloric acid. Add 5 drops of sodium nitrite solution (1 in 10), then 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
Salmonella species and
Escherichia coli and for absence of
Staphylococcus aureus and
Pseudomonas aeruginosa; the total aerobic microbial count is less than 100 cfu per mL.
Assay—
Transfer an accurately measured volume of Otic Solution, equivalent to about 400 mg of benzocaine, to a beaker, add 150 mL of cold 1.6 N hydrochloric acid, and stir until a fine dispersion is obtained. 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.
