The method is applicable to products having sodium contents greater than 0.01 % (m/m). The principle consists in the dissolution of a test portion, followed by acidification to ph value 1. Atomization of the obtained solution in the burner of a flame spectrophotometer. Measurement of the intensity of the radiation emitted at 589 nm; comparison with the intensity obtained for standard sodium chloride solutions, the acidity and potassium chloride content of which are equivalent to that of the test solution. - Cancels and replaces ISO Recommendation R 1550-1970.