Physical properties
White amorphous powder; density 7.41 g/cm
3; dehydrates above 130°C and decomposes at 145°C; slightly soluble in water, 155 mg/L at 20°C; KSP 1.42x10
-20 at 25°C; soluble in dilute acids and alkalies; insoluble in acetone and acetic acid.
Preparation
Lead dioxide is produced by oxidizing an alkaline slurry of lead monoxide with chlorine, sodium hypochlorite, or bleaching powder. Alternatively, it is obtained by passing chlorine into a hot aqueous suspension of lead sulfate and magnesium hydroxide. The ionic reaction is:
Pb(OH)
3ˉ +ClOˉ → PbO
2 + Clˉ+ OHˉ + H
2O
It also is produced by electrolysis of acidic solutions of lead salts using a lead or platinum electrode. In such electrolytic process, lead dioxide is deposited on the anode of the cell.
Insoluble powdered lead dioxide also may be obtained when lead tetroxide is heated with nitric acid:
Pb
3 O
4 + 4HNO
3 → 2Pb(N)
3)
2 + PbO
2 + 2H
2O
Lead dioxide also can be prepared by fusing lead monoxide with a mixture of sodium nitrate and sodium chlorate.
