“…The three major constituents in the mixture additions are usually Ce, La, and Pr and their concentrations in steel range downward to 0.008, 0.005, and <0.005 wt %, respectively (25). Although spark excitation optical emission or X-ray fluorescence techniques for the determination of these elements in steels have been described (26)(27)(28), many of the methods require prior chemical separation of the rare earths. In contrast, these elements can be determined directly in the dissolved steels when the inductively coupled plasma is used as the excitation source, as shown by "This sample was run on a time integration of 20 sec without the internal reference channel.…”