ISO 6918:1984

A test solution is prepared by one of the two following ways: a) fusion of a test portion with sodium carbonate in the case of total calcium and magnesium contents, and b) from an aliquot portion of "solution A" (ISO 2217) for alkali-soluble calcium and magnesium contents. Lanthanum ions are added to the solution to suppress certain interferences. The solution is aspirated into an acetylene/dinitrogen monoxide flame and the measurement are carried out at a wavelength of 422.7 nm (calcium line) and of 285.2 nm (magnesium line).