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electrowinning gold oxygen aqua regia 1

Mar 31, 2021 Aqua Regia HNO 3 3HCl is used to etch gold or platinum. It is a mixture of Nitric acid and Hydrochloric acid that is freshly mixed before use. Optimally it is in a molar ratio of 1 part nitric acid to 3 parts hydrochloric acid. When freshly mixed is clear, turns yellow very quickly and eventually red.