(ben zoe' ik as' id).
» Benzoic Acid contains not less than 99.5 percent and not more than 100.5 percent of C7H6O2, calculated on the anhydrous basis.
Packaging and storage Preserve in well-closed containers.
Identification Prepare a saturated solution of Benzoic Acid in water, and filter twice. To one portion of the filtrate add ferric chloride TS: a salmon-colored precipitate is formed. To a separate 10-mL portion of the filtrate add 1 mL of 7 N sulfuric acid and cool the mixture: a white precipitate forms in about 10 minutes; this precipitate is soluble in ether.
Congealing range 651: between 121 and 123.
Water, Method I 921: not more than 0.7%, a 1 in 2 solution of methanol in pyridine being used as the solvent.
Readily carbonizable substances 271 Dissolve 500 mg in 5 mL of sulfuric acid: the solution has no more color than Matching Fluid Q.
Residue on ignition 281: not more than 0.05%.
Heavy metals 231 Dissolve 2.0 g in 25 mL of acetone, and add 2 mL of water. Add 1.2 mL of thioacetamide-glycerin base TS and 2 mL of pH 3.5 Acetate Buffer, and allow to stand for 5 minutes: any color produced is not darker than that of a control made with 25 mL of acetone, 2.0 mL of Standard Lead Solution, and treated in the same manner. The limit is 10 µg per g.
Readily oxidizable substances Add 1.5 mL of sulfuric acid to 100 mL of water, heat to boiling, and add 0.1 N potassium permanganate, dropwise, until the pink color persists for 30 seconds. Dissolve 1.00 g of Benzoic Acid in the hot solution, and titrate with 0.1 N potassium permanganate VS to a pink color that persists for 15 seconds: not more than 0.50 mL of 0.10 N potassium permanganate is consumed.
Assay Dissolve about 500 mg of Benzoic Acid, accurately weighed, in 25 mL of diluted alcohol that previously has been neutralized with 0.1 N sodium hydroxide, add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS to a pink color. Each mL of 0.1 N sodium hydroxide is equivalent to 12.21 mg of C7H6O2.
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USP35NF30 Page 2325Pharmacopeial Forum: Volume No. 34(5) Page 1147