| Description |
vii, 70 leaves : illustrations ; 29 cm |
| Summary |
"The removal of antimony is one of the important steps in the production of pure lead. The process of removing antimony from impure lead bullion is called "lead softening". The most common method used is to blow air into a bath of impure molten lead. The impurities, primarily antimony, arsenic and tin, if present, are oxidized and form a slag or "dross" which floats on the surface of the lead bath. A considerable amount of lead is oxidized in this step and joins the other oxidized compounds in the dross. This dross is skimmed from the bath of molten lead and the antimony, arsenic and lead are recovered in separate operations. Recovery of the antimony from this slag is difficult and expensive. Therefore, the need for an efficient, cheap process by which the antimony can be recovered from the mixed oxide slag is apparent. The present investigation was made to examine the possibility of recovering the antimony from the slag by use of a vacuum process. Antimony forms a volatile oxide, Sb₂O₃. The lead and lead oxide, PbO, are relatively nonvolatile. Therefore, it should be possible to separate the antimony from the impure lead bullion by selectively volatilizing the antimony as antimony trioxide, Sb₂O₃. To determine if this selective volatilization process is possible, a study was made of the vapor pressures of artificial lead oxide - antimony trioxide mixtures. The antimony trioxide is the only highly volatile phase present in these mixtures, so the vapor pressure is due almost entirely to the antimony trioxide. The vapor pressures were determined for mixtures of PbO -Sb₂O₃ of several different compositions. Additions of silica, SiO₂, were then made to the PbO-Sb₂O₃ mixtures to determine the effect of the silica on the vapor pressures of these mixtures. The silica was expected to form a lead silicate compound and thus prevent the formation of a lead antimonite compound. It was hoped that this would increase the vapor pressures of the Sb₂O₃ above the PbO-Sb₂O₃ -SiO₂ mixtures. The vapor pressures were measured by the inert gas saturation method. For comparison, the volatility of the PbO-Sb₂O₃ mixtures was measured directly by heating the sample under a vacuum"--Introduction, leaves 1-2. |
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