Packaging and storage—
Preserve in tight containers, and preferably store at a temperature not below 15
.
Labeling—
The label of bulk containers of the Solution directs the drug repackager to demonstrate compliance with the USP
Assay limit for formaldehyde of not less than 37.0%, by weight, immediately prior to repackaging.
Identification—
A:
Dilute 2 mL with 10 mL of water in a test tube, and add 1 mL of silver-ammonia-nitrate TS: metallic silver is produced either in the form of a finely divided, gray precipitate, or as a bright, metallic mirror on the sides of the test tube.
B:
Add 2 drops to 5 mL of sulfuric acid in which about 20 mg of salicylic acid has been dissolved, and warm the liquid very gently: a permanent, deep-red color appears.
Acidity—
Measure 20.0 mL into a flask containing 20 mL of water, add 2 drops of
bromothymol blue TS, and titrate with 0.1 N sodium hydroxide VS: not more than 10.0 mL of 0.1 N sodium hydroxide is consumed.
Assay—
Transfer about 3 mL of Solution to a tared flask containing 10 mL of water, insert the stopper in the flask tightly, and accurately determine the weight of the Solution taken. Slowly and quantitatively add a mixture of 50.0 mL of 1 N sodium hydroxide VS and 50 mL of
hydrogen peroxide TS that has been previously neutralized to
bromothymol blue TS with 1 N sodium hydroxide. Heat the contents of the flask cautiously on a steam bath for 15 minutes, shaking it occasionally with a rotary motion. Allow the mixture to cool, rinse the funnel and the inner wall of the flask with water, and after allowing it to stand for 30 minutes, add 2 to 5 drops of
bromothymol blue TS, and titrate the excess alkali with 1 N sulfuric acid VS. Perform a blank determination (see
Residual Titrations under
Titrimetry 
541
). Also make a correction based upon the acidity found in the test for
Acidity. Each mL of 1 N sodium hydroxide is equivalent to 30.03 mg of CH
2O.
