This method is applicable to products having Ca contents greater than 0,003 % (m/m). The principle consists in dissolution of a test portion by the influence of hydrochloric acid under pressure. Addition of sodium ions to promote and to stabilize the emission of calcium, and of lanthanum ions or triethanolamine to increase the sensitivity. Aspiration of the solution into an acetylene-dinitrogen monoxide flame and photometric measurement of the absorption of the 422,7 nm line emitted by a hollow-cathode calcium lamp. For the determination of higher CaO contents (over about 0,03 % (m/m)) an acetylene-air flame can be used. Replaces ISO Recommendation R 2069-1971.