?maximum limit of impurities: Appearance of solution: passes test Insoluble matter in H2O: passes test Residue on ignition (as SO4): 0.1 % Residual solvents (Ph.Eur.): passes test Fumaric Acid: passes test Water (H2O): 1.5 % Heavy metals (as Pb): 0.001% Fe: 0.0005 %