这个过程被称为“置换”，因为溶液溶解了原来的物质，并用等量的新物质取而代之。
This process is termed "replacement" because solutions have dissolved the original material and replaced it with an equal volume of the new substance.
置换后草酸溶液循环使用，降低了成本。
The oxalic acid solution can be re-used through displacement for reducing the cost.
净化过程主要是加入锌粉到溶液，这样所有电位序在锌之后的元素都被置换出来并且凝固沉淀下来。
Purification is mainly done by adding zinc dust to the solution. As all the elements to be removed lie below zinc in the electrochemical series they can be precipitated by cementation.
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