A: Infrared Absorption á197Kñ.

B: Dissolve 0.1g of it in 10mLof water containing 0.1g of sodium nitrite,and add 1mLof 2Nsulfuric acid:a green color is produced.

Assay procedure 1— Transfer about 1500mg of Dichloralphenazone,accurately weighed,to a beaker,add 10mLof water and 20.0mLof 0.5Nsodium hydroxide VS.Allow to stand for 2minutes,and titrate with 0.5Nsulfuric acid VSto a colorless phenolphthalein endpoint.Titrate this neutralized solution with 0.1Nsilver nitrate VS,using potassium chromate TSas the indicator.To the volume of 0.5Nsulfuric acid used in the first titration add four-fifteenths of the volume of 0.1Nsilver nitrate used in the second titration,and subtract the sum obtained from the volume of 0.5Nsodium hydroxide added.Each mLof 0.5Nsodium hydroxide represented by the difference is equivalent to 129.8mg of C15H18Cl6N2O5.

Assay procedure 2— Transfer about 400mg of Dichloralphenazone,accurately weighed,to a 125-mLconical flask,add 20mLof a 1in 10solution of sodium acetate,and swirl to dissolve.Add 25.0mLof 0.1Niodine VS,and allow to stand in the dark for 20minutes,gently swirling occasionally.Add 10mLof chloroform,rinsing the walls of the flask,and swirl until the precipitate is dissolved.Titrate the excess iodine with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Perform a blank titration (see Residual Titrationsunder Titrimetry á541ñ).The difference between the titrations represents the amount of iodine consumed.Each mLof 0.1Niodine consumed is equivalent to 25.95mg of C15H18Cl6N2O5.

Calculation— The difference between the percentages calculated from Assay procedure 1and Assay procedure 2is not more than 1.5%.