... and acid contact is released SO2 generated corresponding salts, long for air, is oxidized to Na2S2O6, reason this product not far ... . Above 1500C, namely the SO2 decomposition.Use:Industrial used for printing and dyeing, organic synthesis, printing, the leather making, ... (As) /%≤0.0001≤0.0002Ferric (Fe)/%≤0.0005≤0.002Heavy metal (Pb)/%≤0.0005≤0.002 high quality sodium metabisulfite Na2S2O5