An optical emission spectrographic method for the determination of niobium in steels

An optical emission spectrographic method for the determination of niobium in steels in the range from 0.1 to 2% Nb is described. The sample is converted to oxide through acid dissolution and mixed with buffer and graphite in the ratio 1:2. The mixture is subjected to dc arc excitation using graphite electrodes. The resulting spectrum is recorded on a Kodak SA-1 emulsion using a Hilger large quartz spectrograph. A pre-arc period of 30 s and an exposure of 30 s are adopted. Two lines of niobium at 2583.986 and 2590.944 A are selected as analysis lines while iron line at 2587.999 A is used as internal standard line. The method shows a mean standard deviation of +- 15%. (author)