ISO 2366:1974

The methods are applicable as alternatives to products for which the molar ratio NaF/AlF3 is equal to about 3. The principle of the flame emission method consists in atomization of the test solution in a flame of oxygen/hydrogen and determination by measurement of the intensity of the radiation at 589 nm. The principle of the flame atomic absorption method is based on atomization in an air/acetylene flame and measuremnt of the absorption of the 589 nm line emitted by a sodium hollow-cathode lamp. The preparation of the test solution is carried out by dissolution of a test portion in hydrochloric acid and water after attack by concentreted sulphuric acid.