C7H6O2 122.12

Benzoic acid.
Benzoic acid [65-85-0].

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-mLportion of the filtrate add 1mLof 7Nsulfuric acid and cool the mixture:a white precipitate forms in about 10minutes;this precipitate is soluble in ether.

Congealing range á651ñ: between 121and 123.

Water,Method Iá921ñ: not more than 0.7%,a 1in 2solution of methanol in pyridine being used as the solvent.

Readily carbonizable substances á271ñ— Dissolve 500mg in 5mLof sulfuric acid TS:the solution has no more color than Matching Fluid Q.

Residue on ignition á281ñ: not more than 0.05%.

Heavy metals á231ñ— Dissolve 2.0g in 25mLof acetone,and add 2mLof water.Add 1.2mLof thioacetamide-glycerin base TSand 2mLof pH3.5Acetate Buffer,and allow to stand for 5minutes:any color produced is not darker than that of a control made with 25mLof acetone,2.0mLof Standard Lead Solution,and treated in the same manner.The limit is 10µg per g.

Readily oxidizable substances— Add 1.5mLof sulfuric acid to 100mLof water,heat to boiling,and add 0.1Npotassium permanganate,dropwise,until the pink color persists for 30seconds.Dissolve 1.00g of Benzoic Acid in the hot solution,and titrate with 0.1Npotassium permanganate VSto a pink color that persists for 15seconds:not more than 0.50mLof 0.10Npotassium permanganate is consumed.

Assay— Dissolve about 500mg of Benzoic Acid,accurately weighed,in 25mLof diluted alcohol that previously has been neutralized with 0.1Nsodium hydroxide,add phenolphthalein TS,and titrate with 0.1Nsodium hydroxide VSto a pink color.Each mLof 0.1Nsodium hydroxide is equivalent to 12.21mg of C7H6O2.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 233

Phone Number:1-301-816-8394