Specification for Industry Grade and Food Grade:
Item Quality Index
Industry Grade Food Grade
Purity ( As Na2SO3) 96.0% min 98.0% min
Sodium sulphate ( SO4) 2.0% max 1.0% max
Chlorides ( As NaCL) 0.5% max 0.1% max
Arsenic ( As ) - 0.0002% max
Heavy metals ( As Pb ) - 0.0005% max
Iron (Fe) 0.005% max 0.002% max
Water insolubles 0.05% max 0.02% max
Item Quality Index

Photo Grade
Pharmaceutical Grade

Purity ( As Na2SO3)
98.0% min
98.0% min

Sodium sulphate ( SO4 )
1.0% max
1.0% max

Chlorides ( As CL - )
0.05% max
0.05% max

Arsenic ( As )
0.0002% max
2ppm max

Lead ( As Pb)
0.0005% max
2ppm max

Iron (Fe)
0.001% max
5ppm max

Selenium ( Se)
0.0001% max
1ppm max

Zinc ( Zn)
0.0001% max
1ppm max

Copper ( Cu )
0.0001% max
0.1ppm max

Mercury ( Hg)
0.0001% max
0.1 ppm max