Appearance A clear, colorless to pale yellow liquid, which becomes brown on storage Specific gravirty 1.5000 g Assay (alkalimetric) 47 - 49% Arsenic (As) Max 0.00005% Chloride (Cl) Max 0.05% Heavy metal (as Pb) Max 0.0005% Iodide (I) Passes test (approx.0.003%) Iron (Fe) Max 0.0001% Organic substances Passes test Phosphate (PO4) Max 0.003% Residue on ignition Max 0.003% Selenium (Se) Passes test (approx.0.01 ppm) Sulphate and Sulphite (as SO4) Max 0.003%