| 摘要 |
<p>Alkali and calcium stannates; lead hydrate.--In a modification of the parent Specification for detinning scrap tin plate, an aqueous solution of lead hydrate in caustic alkali, preferably at or near its boiling point, is used as the detinning agent. The lead hydrate is preferably prepared by adding a solution of lead acetate to caustic alkali solution for example at 70 DEG C. but preferably below 95 DEG C. In a cyclic method of carrying out the invention, the scrap is treated with the detinning agent, air being bubbled through. Calcium stannate is precipitated from the spent solution by milk of lime, caustic alkali formed being reused in the process, and the spongy lead is treated with acetic acid to regenerate lead acetate. The alkali acetate formed with lead hydrate in the first step is treated with sulphuric acid for the recovery of acetic acid. The scrap may first be washed with dilute caustic alkali and roasted to burn off paper and siccatives.ALSO:Metallic lead is precipitated in a process for detinning scrap wherein the scrap plate is treated with a solution of lead hydroxide in caustic alkali. The lead is regenerated by treatment with acetic acid to produce lead acetate, from which lead hydrate is reformed.</p> |
