| 摘要 |
A solution, sol or colloidal dispersion of a substantially water insoluble metal hydroxide or acid and an alkali metal hydroxide are electrodialytically converted to a solid substantially water insoluble metal hydroxide or acid and a solution of the alkali metal hydroxide substantially free of the water insoluble metal hydroxide or acid. The conversion is effected by electrodialysis and electrotransport of an alkali metal cation from the solution, sol or dispersion through a cation permeable membrane into an aqueous alkali hydroxide solution and by using a water soluble anion of an acid to vary pH of the solution sol or dispersion to insolubilize the water insoluble metal hydroxide or acid. Sodium hydroxide etchants of aluminum are continously converted to solid aluminum hydroxide and aqueous sodium hydroxide free of aluminum hydroxide.
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