| 210 / | HD | LIQUID PURIFICATION OR SEPARATION |
| 600 | DF | PROCESSES {14} |
| 660 | DF | .~ Ion exchange or selective sorption {8} |
| 681 | DF | .~.~ Removing ions {4} |
| 683 | | .~.~.~ Anions {2} |
| 684 | DF | .~.~.~.~> Metal complexed (e.g., chromate, ferricyanide, chlorplatinate, etc.) |
| 685 | DF | .~.~.~.~> Including cation {1} |