ISO 2198:1972

Applicable to products having content greater than 0,02 % (m/m). The principle consists in dissolution, in a specified volume of sodium chloride solution saturated at 20 °C, of the total sodium carbonate present in the test portion. Filtration of the insoluble matter which constitutes the major part of the sodium hydrogen carbonate. Titration, in an aliquot part of the filtrate, of the total alkalinity (corresponds to the Na2CO3 and to the more or less constant soluble part of the NaHCO3).Determination of the carbonate content by reading of the attached graph, which gives a direct reading of the difference betwwen the total alkalinity and that part due to the sodium hydrogen carbonate.