Packaging and storage—
Preserve in tight containers, protected from light, and avoid prolonged exposure to temperatures exceeding 30
.
Identification—
Place an amount of Cream, equivalent to about 50 mg of benzocaine, in a small beaker, add 20 mL of 0.5 N hydrochloric acid, warm gently to disperse the Cream, cool, and filter. To 10 mL of the filtrate add 5 drops of a solution of sodium nitrite (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—
Weigh accurately an amount of Cream, equivalent to about 200 mg of benzocaine, in a tared 250-mL beaker. Add 50 mL of water and 5 mL of hydrochloric acid, and stir by mechanical means, with gentle warming, until solution is effected. 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. Each mL of 0.1
M sodium nitrite is equivalent to 16.52 mg of C
9H
11NO
2.
