the manufacturer of sodium metabisulphite, Industry Grade & food Grade Specification:Na2S2O596%minSO265%minAs0.0002%maxHeave Metal (as Pb)0.0005%maxFe0.002%maxWater insoluble0.05%maxPh4.0-4.8 Packing:in 25kg or 50kg plasitc woven bags with polyethylene liner,paper-plastic composite bag,kraft bag Storage: in dry and cool warehouse with package sealed and away from rain and water.