Appearance White crystalline powder Assay Min 99.5% Melting point 185 - 190 deg C Insoluble matter Max 0.003% Sulphated ash Max 0.01% Chloride (Cl) Max 0.001% Sulphate (SO4) Max 0.002% Ammonium (NH4) Max 0.001% Copper (Cu) Max 0.0005% Iron (Fe) Max 0.0005% Lead (Pb) Max 0.0005% Substance reducing KMnO4 (as O) Max 0.008%