Commonly Antimony trioxide Antimony Trioxide HS Code: 2825800000. CAS No.:1309-64-4. Antimony Trioxide UN No.: 1549. Item Sb2O3 Sb2O3 99.8 99.5 Chemical composition Sb2O3% (min) 99.8 99.5 Impurity As2O3 0.05 0.06 ≤ PbO 0.08 0.1 Fe2O3 0.005 0.006 CuO 0.002 0.005 Se 0.004 0.002 Physical property White degree 96 95 Average size (µm) 0.3-0.9 0.9-1.1