Collect all the liquids holding copper in a large cask filled with wrought or cast iron scraps; a chemical reaction immediately takes place, the iron is substituted for the copper to make a soluble salt, and copper falls to the bottom of the cask in the shape of a brown powder. The cask should be large enough to hold all the liquids employed in a day's work. The iron scrap should be suspended in willow baskets on the top of the liquor, and, by stirring now and then the liquid with them, the metallic powder of copper will alone fall to the bottom of the cask. The same method may be employed for recovering the copper from old cleansing acids, or from worn out galvanoplastic baths. The copper thus obtained is quite pure; calcining it in contact with the air, gives a black binoxide of copper for neutralising too acid galvanoplastic baths.