Appearance A clear colorless liquid Assay (alkalimetric) 48.0-51.0% Sulphate and Sulphite (as SO4) Max 0.0005% Phosphate (PO4) max 0.0001% Fluorosilicic acid (H2SiF6) max 0.01% Residue on ignition max 0.0005% Chloride (Cl) Max 0.0005% Iron (Fe) Max 0.0001% Heavy metal (as Pb) max 0.00005% Arsenic (As) Max 0.000005% Copper (Cu) Max 0.00001%