Packaging and storage—
Preserve in well-closed containers.
Identification—
B:
Shake 1 g of it with 10 mL of water, and filter. To the filtrate add 1 mL of
ferric chloride TS: an intense reddish violet color is produced. To this solution add 1 mL of acetic acid: the color is not dispersed. To this solution add 2 mL of 2 N hydrochloric acid: the color is dispersed and a white crystalline precipitate is formed.
Assay for zinc oxide—
Weigh accurately in a tared porcelain crucible about 500 mg of Paste, heat gently until melted, and continue the heating, gradually raising the temperature until the mass is thoroughly charred. Ignite the mass strongly until all of the carbonaceous material has been dissipated, the residue is uniformly yellow, and the weight of the cooled residue is constant. The weight of the residue represents the quantity of ZnO in the weight of the Paste taken for the assay.
Assay for salicylic acid—
Transfer to a suitable beaker about 5 g of Paste, accurately weighed. Add 40 mL of alcohol, previously neutralized with 0.1 N sodium hydroxide to a phenol red endpoint, and heat on a water bath for 5 minutes, with frequent swirling. While still hot, add phenol red TS, and titrate with 0.1 N sodium hydroxide VS to a red endpoint. Each mL of 0.1 N sodium hydroxide is equivalent to 13.81 mg of salicylic acid (C7H6O3).
to make
755
:
meets the requirements.