Applicable to products having a residue of equal to or more than 0.02 % (m/m). For products obtained in modern plants this evaluation is not usually required. Indicates to the risk in handling with this product. Analysis by evaporation, at ambient temperature, of a test portion and weighing of the residue. Titration of the ammonia contained in the residue with standard volumetric sulphuric acid solution in the presence of an indicator. Subtraction of this mass from that of the redidue. A typical apparatus for the test is shown in a figure.