Applicable to the analysis of products having contents either above 0.1 % (m/m) or above 0.25 % (m/m) according to whether the product is readily or sparingly soluble in water. The principle consists in dissolution of a test portion either directly or after alkaline fusion. Separation of the insoluble matter. Precipitation, while boiling, of the sulphate ions in an acid medium. Filtration, washing and calcination of the precipitate. Weighing of the barium sulphate after treatment with hydrofluoric acid in order to remove any silica which may be present. Has also been approved by the IUPAC.