The method generally adopted commercially of purifying zinc is to melt the metal in a reverberatory furnace having an inclined bed, in which the metal collects, and the lead, being of heavier specific gravity, falls to the bottom. This allows the impurities to oxidise and form a scum on the top of the metal. Of course, the metal is kept just at melting point, otherwise a large loss of zinc by volatilisation results. It is practically impossible to purify zinc on a small scale. A plan that might be tried (although its success cannot be guaranteed) would be to melt the zinc under a thick layer of flour charcoal. Should there be any bismuth or arsenic in the metal, these impurities might be driven off, as they volatilise at a much lower temperature than zinc. Lead, which would be the largest impurity, would separate out and would be poured last, so that the major portion of the zinc would be comparatively pure.