Appearance White crystals or crystalline powder Chloride (Cl) Not more than 0.04% Ammonium (NH4) Not more than 0.02% Iron (Fe) Not more than 30ppm Heavy metal(Pb) Not more than 10ppm Arsenic(As2O3) Not more than 2ppm Loss on drying Not more than 0.60% Residue on ignition(sulfated) Not more than 0.20% Assay 98.0 to101.0% pH 2.5 to 3.5