This standard applies to the determination of calcium, mg and sodium in cobalt oxalate, and the determination range is 0.001% to 0.01%, respectively. After the sample is analyzed for nitric acid, the Absorbance of each element is determined at different wavelengths by Flame Atomic Absorption Spectrometer (FAAS), and the content of calcium, mg and sodium is calculated by the standard Linear dispersion method of cobalt matrix. The standard describes the reagent preparation, instrument calibration and experimental operation procedures in detail, providing scientific guidance for the experiment.