Applicable to products having a Ca content of more than 50 mg/kg. Soluble SiO2 present in the solution at levels lower than 5 g/ml does not interfere. The principle consists in addition, to a hydrochloric acid solution of the test portion, of sodium ions to promote and stabilize the emission of calcium and of lanthanum ions to suppress the interference of aluminium. Specifies the aspiration of the solution into an acetylene-dinitrogen monoxide flame. Photometric measurement of the absorption of the 422.7-nm line emitted by a hollow- cathode calcium lamp. Has also been approved by the IUPAC.