| 423 / | HD | CHEMISTRY OF INORGANIC COMPOUNDS |
| 351 | DF | NITROGEN OR COMPOUND THEREOF (EXCEPT AMMONIUM SALT OF NON-NITROGEN ACID) {5} |
| 385 | | .~ Oxygen containing {4} |
| 386 | DF | .~.~> Halogen containing |
| 387 | DF | .~.~> Hydrogen containing {2} |
| 395 | DF | .~.~> Nitrate {3} |
| 400 | DF | .~.~> Binary compound (oxide of nitrogen) {3} |