Abstract
In order to obtain an extra pure copper the zone refining process has been applied to vacuum-melted copper. Some technical problems on zone refining were also discussed on the basis of the results of preliminary experiments. The following results were obtained on the ingot zone refined by sixteen passes of the molten zone. (1) Ag, Si, Mn, As, Pb and Sn in the original copper were concentrated markedly to the direction of travel of the molten zone but Al and Fe were not concentrated while Ca and Mg were distributed irregularly. (2) It was assertained by a qualitative spectrographic analysis that the purity of the most refined part was much higher than that of the Johnson Matthey’s spectrographically standardized copper (99.999%). (3) The electrical resistivity of the purest part was 1.667±0.002 μΩ cm (at 20°C) after annealing. (4) In the case of highly cold-drawn wires of zone-refined copper, a decrease of electrical resistivity was observed by annealing even at room temperature for long time, which seems to be dependent upon the high purity of the wires.
