Appearance White crystalline powder Assay (alkalimetric) 99.5 - 100.5% Identity (IR) Passes test Chloride (Cl) Max 0.001% Insoluble matter in water Max 0.005% Iron (Fe) Max 0.0003% Sulphate (SO4) Max 0.005% Phosphate (PO4) Max 0.001% Heavy metal (as Pb) Max 0.0005% Arsenic (As) Max 0.0001% Mercury (Hg) Max 0.0001% Lead (Pb) Max 0.0002% Oxalate (as C2H2O4) Passes test Sulphated ash (at 600°C) Max 0.05% Substance carbonizable by hot H2SO4 Passes test Water (by KF) Max 0.5%