» Nitromersol, dried at 105 for 2 hours, contains not less than 98.0 percent and not more than 100.5 percent of C7H5HgNO3.
Packaging and storage Preserve in tight, light-resistant containers.
A: A solution (1 in 1000) in 1 N sodium hydroxide possesses a reddish-orange color. The addition of 3 N hydrochloric acid to this solution causes the color to disappear and a yellowish, flocculent precipitate to form.
B: To a solution prepared by dissolving 250 mg of Nitromersol in 2.5 mL of 1 N sodium hydroxide and diluting with water to 20 mL add about 3 mL of 3 N hydrochloric acid: a yellowish precipitate is formed. Upon filtration, the filtrate is nearly colorless or slightly yellow. Retain the filtrate for the test for Mercury ions. Dissolve the precipitate in 20 mL of water to which 2.5 mL of 1 N sodium hydroxide has been added, add 0.5 g of sodium hydrosulfite, and heat to boiling: a heavy deposit of metallic mercury is formed.
Loss on drying 731 Dry it at 105 for 2 hours: it loses not more than 1.0% of its weight.
Residue on ignition 281: not more than 0.1%.
Mercury ions To the filtrate obtained in Identification test B add an equal volume of hydrogen sulfide TS: no darkening in color is produced, although a small amount of a flocculent, light yellow precipitate may form.
Alkali-insoluble substances Add 7 mL of 1 N sodium hydroxide to 1.0 g of Nitromersol, then dilute with water to 20 mL. The resulting solution, upon standing in a glass-stoppered vessel in the dark for 24 hours, shows no more than a slight amount of insoluble material. Collect the insoluble residue, if any, in a tared filter crucible, wash the residue with warm water, and dry at 105 for 1 hour: the weight of the insoluble material does not exceed 1 mg (0.1%).
Uncombined nitrocresol Shake 500 mg of Nitromersol with 50 mL of benzene, filter, evaporate the filtrate in a tared dish to dryness, and dry the residue at 80 for 2 hours: the weight of the residue does not exceed 5 mg (1%).
Assay Weigh accurately about 200 mg of Nitromersol, previously ground to a fine powder and dried, and transfer to a 500-mL Kjeldahl flask. Add 15 mL of sulfuric acid, digest cautiously with occasional swirling over a flame until the solution becomes a clear, light yellowish brown, cool, and add, dropwise, enough 30 percent hydrogen peroxide to decolorize the solution. Digest for 2 to 3 minutes, adding more hydrogen peroxide, if necessary, to produce a colorless solution. Cool, dilute with water to about 100 mL, and add potassium permanganate TS until a permanent pink color persists on heating. Then add hydrogen peroxide TS, dropwise, until the color is completely discharged. Cool, and add 5 mL of nitric acid which has been diluted with 10 mL of water. Add 5 mL of ferric ammonium sulfate TS, and titrate with 0.1 N ammonium thiocyanate VS. Each mL of 0.1 N ammonium thiocyanate is equivalent to 17.59 mg of C7H5HgNO3.