Our company's specification:

Sodium sulfite ( as SO2),%...............................................................65.0 Min

Fe % ...........................................................................................  .0.005 Max

Water-insoluble Matters %................................................................0.05 Max

Heavy metal (Pb) %..........................................................................0.002 Max

Arsenic ( As) %........................................................................... ....0.0002 Max

Appearance............................................................            ..... White or tiny yellow crystal or crystal powder

PH................................................................................................   . 4.0-4.6