An impure sample of Na3PO3 weighing 0.1392 g was dissolved in 25 mL of water. A solution containing 50 mL of 3% w/v mercury(II) chloride, 20 mL of 10% w/v sodium acetate, and 5 mL of glacial acetic acid was then prepared. The solution containing the phosphite was added dropwise to the second solution, oxidizing PO3^3– to PO4^3– and precipitating Hg2Cl2. After digesting, filtering, and rinsing, the precipitated Hg2Cl2 was found to weigh 0.4320 g. Report the purity of the original sample as %w/w Na3PO3.