When working with low-grade copper ores, bacteria or acids are utilised to leach the copper in the presence of air. Copper is introduced to the solution as  Cu²⁺ ions in this method:

Cu + 2H⁺ + ½ O₂ ⇒ Cu²⁺ + 2H₂O

The solution so obtained is then treated with H­₂ or scrap iron to get copper metal.

Cu + 2H⁺ ⇒ 2H²⁺ + Cu