Chemical Specifications Appearance Deep red crystals Assay (complexometric) 97 - 102% Nitrate (NO3) Max 0.05% Sulphate (SO4) Max 0.05% Iron (Fe) Max 0.05% Nickel (Ni) Max 0.15% Zinc (Zn) Max 0.1% Substance not precipitated by ammonium sulphide (as SO4) Max 0.3%