This standard specifies a method for the determination of dissolved calcium and magnesium by flame atomic absorption spectrometry. It is intended for the analysis of raw and drinking waters and can be used for waters having a calcium content of up to 50 mg/l and a magnesium content of up to 5 mg/l. For samples containing higher concentrations of calcium or magnesium a smaller volume of the sample must be taken for the analysis. When using the air/acetylene flame and the dilution factor 1 in 10, as described in 6.1, the optimum range is 3 to 50 mg/l for calcium and 0,9 to 5 mg/l for magnesium