| 568 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {4} |
| 300 | DF | .~ OXYGEN CONTAINING (E.G., PERCHLORYLBENZENE, ETC.) {11} |
| 420 | DF | .~.~ Aldehydes {8} |
| 448 | DF | .~.~.~ Acyclic {4} |
| 449 | DF | .~.~.~.~ Processes {14} |
| 492 | DF | .~.~.~.~.~ Purification or recovery {1} |
| 493 | | .~.~.~.~.~.~ Of formaldehyde per se |