Reactive metals, such as ce and la, are difficult to obtain in a pure state because of high melting point and reactivity, but bars of some of their alloys having a lower melting point are more easily prepared with small impurity contents, which can be concentrated at one end of the bar with much of the alloying elements by electrotransport, leaving the other end in a more pure state. Bars 6 in long and 0.5 In diam of impure ce and la were treated by passing a heavy direct current through them lengthwise for 100 h at 600 deg. C in a he atmosphere within a water-cooled enclosure to prevent overheating. Only 400 a could be used steadily without danger of fusion by resistance heating, but by pulsing the current, 1,200 a could be used for 6 s combined with 54 s of cooling for each minute of the test period. The ends of the specimen were analyzed, the ce bars for mo, cu, o, fe, and mn, and the la bars for mo, cu, c, and fe. A steady 400-a current was relatively inefficient, but the pulsed heavy d.C. Was more efficient. Some effective results on ce were a reduction of cu content at the anode end to 0.07 From 0.47 pct; of 0 to 0.009 pct at the cathode from 0.016 pct; and mn to 0.01 pct at the cathode from 0.07 pct. Similarly on la, cu was decreased to 0.08 pct at the anode end from 0.46 pct; mo to 0.099 pct at the anode from 0.15 pct; and fe to 0.037 pct at the cathode from 0.31 pct. At the opposite ends of the bars, the impurity contents in each instance were correspondingly increased from the respective initial values.
U.S. Pat. 3,650,931; Mar. 21, 1972; Chem. Abstr. 76:156,993F