Identification—
A:
To 1 mL of Topical Solution add 1 mL of 1 N sodium hydroxide, and add, in the order named, 0.5 mL of
potassium iodide TS, 0.5 mL of 3 N hydrochloric acid, and 0.5 mL of
sodium hypochlorite TS: a brown precipitate is formed.
B:
To 1 mL of Topical Solution add 2 mL of 3 N hydrochloric acid, and cool to about 10
. Add 1 mL of sodium nitrite solution (1 in 100), then add a solution prepared by mixing 50 mg of 2-naphthol with 3 mL of sodium hydroxide solution (1 in 10): a red color is produced.
Assay—
Transfer 5 mL of Topical Solution, accurately measured, to a suitable open vessel, evaporate on a steam bath to dryness, and proceed as directed under
Nitrite Titration 
451
, beginning with “Add 20 mL of hydrochloric acid.” Each mL of 0.1
M sodium nitrite is equivalent to 13.71 mg of C
7H
7NO
2.
