ISO 3332:1975

Ammonium sulphate for industrial use — Determination of ammoniacal nitrogen content — Titrimetric method after distillation

Based on dissolution of a test sample in water, distillation of the ammonia after displacement by an alkali solution. Absorption in an excess of standard volumetric sulphuric acid solution and back-titration with standard volumetric sodium hydroxide solution in the presence of methyl red/methylene blue mixed indicator. A typical distillation apparatus is shown in a figure.