| 23 / | HD | CHEMISTRY: PHYSICAL PROCESSES |
| 293 R | DF | PHYSICAL PROCESSES {7} |
| 295 R | DF | .~ Crystallization {8} |
| 305 R | | .~.~ Heavy metal or aluminum compounds {3} |
| 305 A | DF | .~.~.~> Aluminum compounds |
| 305 F | DF | .~.~.~> Iron compounds |
| 305 RE | DF | .~.~.~> Rare earth compounds |