In a previous work, concentrations of fifteen residual elements (Al, B, Co, Cu, Cr, Mo, Nb, Ni, Pb, Sn, Ti, Ta, V, W, Zr) in iron and steel were determined emission-spectrographically to 10 ppm by the metallic block sample technique.As the concentration of ten impurity elements (Al, Ca, Co, Cr, Cu, Mg, Mn, Mo, Ni, V) in pure iron is usually lower than 10 ppm, a study is made to raise the accuracy of emission spectrographic analysis by the powder d-c arc technique.The samples are changed into iron oxides, weighed, and mixed with graphite powder three times as much as the sample.With standard samples of less than 10 ppm impurity contents made by adding known small amounts of impurity elements to pure iron, nine elements except Mo out of the above 10 elements were measurable to 1 ppm with error of less than 10%on obtained figures of the order of 0.001%.
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