?maximum limit of impurities: Appearance of solution: passes test Chloride (Cl): 0.0006 % Sulfate (SO4) (Ph. Eur.): 0.0010 % Sulfate (SO4) (USP-NF): passes test Precipitated substances by NH4OH: passes test Residual solvents (Ph.Eur/USP): passes test Nitrate (NO3): passes test Hypophosphorous and phosphorous acid: passes test Alkaline phosphates: passes test Fe: 0.0006 %