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- $ N{a^ + },{\\\text{ }}{K^ + }$.
- $ M{g^{2 + }},{\\\text{ }}C{a^{2 + }}$.
- $ HC{O_3}^ - ,{\\\text{ }}C{l^ - }$.
- $ S{O_4}^{2 - },{\\\text{ }}C{l^ - }$.