... Powder 4.50kgs in iron drums Sodium hydrosulfite 85%88%90%1) We are second biggest manufacturer in China 2) ... Method: Sodium Formate Process3)Specifications:ItemsIndexTech GradeFood GradeNa2S2O4, % ≥85%88%90%85%Fe, ppm ≤202020---Zn, ppm ≤1111As, ppm ≤---------1Heavy ... Metal(as Pb), ppm ≤---------1Water Insolubles, % ≤0.40.40.050.054)Package: ...