The purification of a solution by passing carbon dioxide through it is called carbonation.

Here's why:

* Carbonation refers to the process of dissolving carbon dioxide in a liquid, usually water.

* This process can lead to the formation of carbonic acid (H2CO3), which can then react with impurities in the solution.

* This reaction can result in the precipitation of certain impurities, making the solution cleaner.

Note: Carbonation is not a universal purification method. It is effective for specific types of impurities, often those that react with carbonic acid to form insoluble compounds.