If the coins were just discolored because of dirt, the detergent would wash the dirt away and make them shiny.Because you need to remove a layer of copper oxide, you need to make a strong acid.

 
  • 如果钱币因肮脏而变色,洗洁剂即可将它们洗净并变得闪亮,要去除那层铜氧化物则需强酸帮忙。
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