Appearance Colourless to brown fuming liquid Assay (as HI) Min 55% Arsenic (As) Max 0.0005% Chloride & bromide (as Cl) Max 0.05% Heavy metal (as Pb) Max 0.001% Iron (Fe) Max 0.001% Stabilizer (H3PO2) Max 1.5% Sulphate (SO4) Max 0.005%