Chemical Specifications Appearance Reddish brown to dark brown crystalline powder Assay (as Fe) 20.5 - 22.5% Chloride (Cl) Max 0.25% Sulphate (SO4) Max 0.3% Heavy metal (as Pb) Max 0.003% Arsenic (As) Max 0.0004% Zinc (Zn) Max 0.005% Free ferric compounds Passes test