Appearance White to Off-White or Pale Yellow Crystals or Crystalline Powder and/or Chunks Assay 99.5 - 100.2% Insoluble matter in water Passes test Sulphated ash Max 0.05% Chloride & bromide (as Cl) Max 0.01% Iodide (I) Max 0.0005% Nitrogen compounds (as N) Max 0.005% Sulphate (SO4) Max 0.02% Copper (Cu) Max 0.001% Iron (Fe) Max 0.001% Lead (Pb) Max 0.001%