C6H8AsNO3 --- 217.05 p-Aminobenzenearsonic acid [98-50-0]. Arsanilic Acid contains not less than 98.0 percent and not more than 102.0 percent of C6H8AsNO3, calculated on the dried basis. Labeling: Label it to indicate that it is for veterinary use only. Identification: Infrared Absorption 197K . Loss on drying: Dry it in vacuum at 80C for 4 hours: it loses not more than 0.5% of its weight. Limit of o-arsanilic acid: To pass the chromatographic test: not more than 0.12% is found. Limit of aniline: pass the chromatographic test: not more than 0.045% is found. Assay: Transfer about 125 mg of Arsanilic Acid, accurately weighed, to a 50-mL conical flask, and add 10.0 mL of a mixture of sulfuric acid, nitric acid, and perchloric acid (1000:50:50) and several glass beads. Digest on a hot plate for about 1 hour, increasing the temperature of the hot plate in steps until a ring of sulfuric acid rises into the neck of the flask. Allow to cool, to the colorless solution add about 400 mg of hydrazine sulfate, and heat the flask vigorously on a hot plate until a ring of sulfuric acid rises into the neck of the flask. Allow to cool, and wash down the rim, neck, and insides of the flask with about 1 mL of water. Heat the flask again until a ring of sulfuric acid rises into the neck of the flask. Allow to cool, and transfer the colorless solution, with the aid of about 80 mL of water, to a 125-mL conical flask. Add 10 mL of hydrochloric acid and several drops of 0.002 M potassium iodide, cool to between 0C and 5C and titrate with 0.1 N potassium permanganate to a pale pink endpoint, maintaining the temperature between 0C and 5C during the titration. Perform a blank determination and make any necessary correction. Each mL of 0.1 N potassium permanganate is equivalent to 10.852 mg of C6H8AsNO3.
