| 423 / | HD | CHEMISTRY OF INORGANIC COMPOUNDS |
| 351 | DF | NITROGEN OR COMPOUND THEREOF (EXCEPT AMMONIUM SALT OF NON-NITROGEN ACID) {5} |
| 352 | DF | .~ Ammonia or ammonium hydroxide {6} |
| 359 | | .~.~ From elemental hydrogen and nitrogen {3} |
| 360 | DF | .~.~.~> With exchanging heat between catalyst and synthesis or effluent gas |
| 361 | DF | .~.~.~> Utilizing plurality of catalyst beds or portions |
| 362 | DF | .~.~.~> Utilizing metal containing catalyst {1} |