| 423 / | HD | CHEMISTRY OF INORGANIC COMPOUNDS |
| 351 | DF | NITROGEN OR COMPOUND THEREOF (EXCEPT AMMONIUM SALT OF NON-NITROGEN ACID) {5} |
| 385 | DF | .~ Oxygen containing {4} |
| 387 | DF | .~.~ Hydrogen containing {2} |
| 390.1 | DF | .~.~.~ Nitric acid {4} |
| 393 | DF | .~.~.~.~ Utilizing nitrogen oxide as reactant {1} |
| 394 | | .~.~.~.~.~ Nitrogen peroxide |