| 摘要 |
<p>Germanium is extracted as its tetrachloride from flue dust by treating it with one to two times the theoretical quantity of hydrofluoric acid to convert all the silica present to silicon tetrafluoride, with or without the addition of sulphuric acid or an acid sulphate, heating the mixture to dryness to drive off the resulting silicon tetrafluoride and thereafter treating the residue with hydrochloric acid and distilling off the germanium tetrachloride, preferably in a stream of chlorine. The hydrofluoric acid may be added to the flue dust and the mixture stirred until the reaction almost ceases before the addition of sulphuric acid or an acid sulphate. If desired the hydrofluoric acid may be formed in situ by the addition to the flue dust of a fluoride such as sodium fluoride, together with sulphuric acid and if excess of the latter remains after the initial treatment of the flue dust the hydrochloric acid for the subsequent treatment may be formed in stiu by adding a metallic chloride such as sodium chloride. As a modification, the acid treated flue dust is heated to dryness as before and the residue is leached with water, the germanium taken into solution is precipitated and separated for example by treatment with sodium carbonate, and the germanium containing precipitate is treated with hydrochloric acid and the germanium tetrachloride distilled. The silicon tetrafluoride evolved in the first stage of the process may be treated with aqueous carbonate of ammonia and the hydrated silica precipitated to leave a solution of ammonium fluoride which may be treated with a soluble sodium salt to precipitate sodium fluoride. The residue remaining after distillation of the germanium tetrachloride contains gallium trichloride which may be extracted by known means.</p> |
