| 摘要 |
PROBLEM TO BE SOLVED: To remove harmful materials as mush as possible while restraining the loss of desired noble metals to the minimum by treating a contcetrete at a high temperature with gaseous hydrogen chloride to obtain a first residue, if necessary, treating the first residue with gaseous chloride to obtain a second residue, treating the first residue or the second residue at a high temp. with oxygen and further treating this material at a high temperature with hydrogen. SOLUTION: A solid raw material is exposed to a chloride atmosphere composed of the gaseous hydrogen chloride. The temperature range is held to 750-1,100 deg.C. This atmosphere forms stable base metal chlorides and a large part of the base metal chlorides can be removed by vaporization. Before oxidizing treatment, the heating furnace is scavenged with inert gas, ordinarily nitrogen. Under the presence of the oxygen, an amphoteric elements which tend to have deleterious effects, e.g. selium, tellurium and arsenic, are removed as metallic oxides thereof. The temperature range for executing this operation is 750-1100 deg.C. Some kinds of materials, e.g. rhodium oxide, can be reduced at a lower temperature of e.g. 200-300 deg.C.
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