Item Quality Index Food Grade Industry Grade Purity ( As Na2S2O5)98.0% min 96.0% min Sulfur Dioxide( SO2) 65.0% min 65.0% min Arsenic ( As ) 0.0002% max - Heavy metals ( As Pb ) 0.0005% max - Selenium (Se ) 0.0005% max - Iron (Fe) 0.001% max 0.002% max Water insoluble0.02% max 0.05% max PH value : 4.0-4.8 4.0-4.8 Remark : Conformed with FCC V and E 223 Standard Packed in 25kg plastic woven bag, 25kg Kraft paper bag, 25kg PE bag, 500kg/1000kg/1100kg/1200kg jumbo bag or as per the buyer's requirement.