Sodium metabisulfite Na2S2O5: 96%min Fe: 0.005% Max Heavy metals(pb):0.001% MAX As: 0.0002%  

Inspection Item	Guaranteed Value	Typical Value
PURITY (AS Na2S2O5):	96.0% MIN	97.15%
ARSENIC (AS) :	-------------	------------
HEAVY METAL (AS Pb) :	-------------	0.0005
WATER INSOLUBLE  :	0.05%MAX	0.0008%
IRON (Fe)  :	0.005%MAX	0.002%
PH VALUE:	4.0--4.6	4.5

Sodium metabisulfite -Industrial grade

sodium metabisulphite