0.06005A/W

for cellulose acetate labeled to contain not more than 42.0% of acetyl groups— Transfer about 2 g, accurately weighed, to a 500-mL flask. Add 100 mL of acetone and 5 mL to 10 mL of water to the flask, insert the stopper into the flask, and stir with a magnetic stirrer until solution is complete. Add 30 mL, accurately measured, of 1.0 N sodium hydroxide VS to the solution, with constant stirring. A finely divided precipitate of regenerated cellulose, free from lumps, is obtained. Insert the stopper into the flask, and stir with a magnetic stirrer for 30 minutes. Add 100 mL of water that has been preheated to 80º, washing down the sides of the flask, stir for 2 minutes, and cool to room temperature. Titrate the excess sodium hydroxide solution with 1.0 N sulfuric acid VS to a phenolphthalein endpoint. Treat a blank in the same manner. Calculate the percentage of acetyl in the portion of Cellulose Acetate taken by the formula: in which B and A are the volumes, in mL, of 1.0 N sulfuric acid consumed by the blank and the Cellulose Acetate, respectively; and W is the weight, in g, of Cellulose Acetate taken, calculated on the dried basis.

for cellulose acetate labeled to contain more than 42.0% of acetyl groups— Transfer about 2 g, accurately weighed, to a 500-mL conical flask. Add 30.0 mL of dimethyl sulfoxide and 100 mL of acetone, and stir for 16 hours with the aid of a magnetic stirrer. Pipet 30 mL of 1 N sodium hydroxide VS slowly into the flask, with constant stirring. Insert the stopper into the flask, and stir for 6 minutes. Allow to stand without stirring for 60 minutes. Resume stirring, and add 100 mL of water that has been preheated to 80º, washing down the sides of the flask. Stir for 2 minutes, and cool to room temperature. Add 4 to 5 drops of phenolphthalein TS, and titrate the excess sodium hydroxide solution with 0.5 N hydrochloric acid VS. Add an accurately measured excess of about 0.5 mL of 0.5 N hydrochloric acid VS. Stir for 5 minutes. Allow to stand for 30 minutes. Titrate with 0.5 N sodium hydroxide VS to a persistent pink endpoint, using a magnetic stirrer for agitation. Calculate the net number of milliequivalents of sodium hydroxide consumed, and correct this value by use of the average of two blank determinations run concomitantly through the entire procedure. Calculate the percentage of acetyl in the portion of Cellulose Acetate taken by the formula: in which n is the corrected value of the net number of milliequivalents of sodium hydroxide consumed; and W is the weight, in g, of Cellulose Acetate taken, calculated on the dried basis.