Appearance A clear colourless liquid Colour scale Max 10 APHA Assay 69 - 72% Chloride (Cl) Max 0.001% Heavy metal (as Pb) Max 0.0001% Iron (Fe) Max 0.0001% Nitrogen compounds (as N) Max 0.001% Residue on ignition Max 0.003% Silicate and phosphates (as SiO2) Max 0.0005% Sulphate (SO4) Max 0.001%