Appearance White to yellow to beige to grey powder or crystals Chloride (Cl) Max 0.005% Sulphate (SO4) Max 0.01% Total nitrogen (N) Max 0.002% Lead (Pb) Max 0.002% Iron (Fe) Max 0.002% Potassium (K) Max 0.02% Copper (Cu) Max 0.001% Sodium (Na) Max 0.02% Loss on ignition (at 750°C) Max 17%