» Sulfathiazole contains not less than 99.0 percent and not more than 100.5 percent of C9H9N3O2S2, calculated on the dried basis.
Packaging and storage Preserve in well-closed, light-resistant containers.
B: To 100 mg add 5 mL of 3 N hydrochloric acid, and boil gently for about 5 minutes. Cool in an ice bath, add 4 mL of sodium nitrite solution (1 in 100), dilute with water to 10 mL, and place the mixture in an ice bath for 10 minutes. To 5 mL of the cooled mixture add a solution of 50 mg of 2-naphthol in 2 mL of sodium hydroxide solution (1 in 10): an orange-red precipitate is formed, and it darkens on standing.
Melting range, Class I 741: between 200 and 204.
Acidity Digest 2 g with 100 mL of water at about 70 for 5 minutes, cool at once to about 20, and filter. Titrate 25 mL of the filtrate with 0.10 N sodium hydroxide, using 2 drops of phenolphthalein TS as the indicator: not more than 0.5 mL is required to produce a pink color. (Retain the remainder of the filtrate for the tests for Chloride 221 and for Sulfate 221.)
Loss on drying 731 Dry it at 105 for 2 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Chloride 221 A 25-mL portion of the filtrate prepared as directed in the test for Acidity shows no more chloride than corresponds to 0.10 mL of 0.020 N hydrochloric acid (0.014%).
Sulfate 221 A 25-mL portion of the filtrate prepared as directed in the test for Acidity shows no more sulfate than corresponds to 0.2 mL of 0.02 N sulfuric acid (0.04%).
Heavy metals, Method II 231: 0.002%.
Ordinary impurities 466
Test solution: methanol.
Standard solution: methanol.
Eluant: a mixture of 1-propanol and 1 N ammonium hydroxide (22:3).
Assay Proceed with Sulfathiazole as directed under Nitrite Titration 451. Each mL of 0.1 M sodium nitrite is equivalent to 25.53 mg of C9H9N3O2S2.
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USP32NF27 Page 3633