| 摘要 |
<p>A solution of alkali metal stannate and/or stannite, formed by dissolving the tin from a tin-coated metal with a solution of (e.g. 5-10 per cent) caustic alkali into which (in the case of stannate) carbon dioxide-free air or oxygen is passed, is treated with an alkali earth metal hydroxide to produce the insoluble alkaline earth stannate, and/or stannite (e.g. barium stannate) which is removed, and the remaining solution recycled. The precipitated salt may be treated with sulphuric acid solution to form barium sulphate and stannous or stannic sulphate or with an alkali metal sulphate to form barium sulphate and alkali metal stannate or stannite, or with hydrochloric acid solution in the stoichiometric amount required to form alkaline earth metal chloride and to free tin as more or less hydrated oxide.ALSO:A tin coating, together with its corrosion products is removed from the metallic base by reacting the coated article with a solution of caustic alkali and removing tin from the resulting solution by addition of one or more of the alkaline earth hydroxides, the solution freed from the tin being recycled without further treatment to the tin dissolving stage.</p> |
