The method can be applied provided the Fe203 content does not exceed 0,15 . It can also be applied to products with molar ratio of NaF to AlF3 between approximately 3 and 1,7. The principle consists in dissolution of a test portion by acid fusion using potassium pyrosulphate and recovery by hydrochloric acid. Separation of the mixture by precipitation of aluminium, with ammonium benzoate , in an acetic reducing medium. Dissolution of the precipitate and reprecipitation as aluminium tri(quinolin-8-oxide) in an acetic buffer medium. Filtration, washing, drying of the precipitate at a temperature of 130 °C and weighing.