Chemical Specifications Appearance White crystalline powder Assay (alkalimetric) Min 99.0% Substance insoluble in Na2CO3 solution Max 0.05% Iron (Fe) Max 0.001% Chloride (Cl) Max 0.005% Sulphate (SO4) Max 0.005% Nitrate (NO3) Max 0.005% Heavy metal (as Pb) Max 0.001% Water (H2O) Max 0.5% Sulphated ash Max 0.02%