| 423 / | HD | CHEMISTRY OF INORGANIC COMPOUNDS |
| 511 | DF | SULFUR OR COMPOUND THEREOF {4} |
| 512.1 | DF | .~ Oxygen containing {11} |
| 544 | DF | .~.~ Sulfate {7} |
| 545 | DF | .~.~.~ Ammonium containing {4} |
| 549 | | .~.~.~.~ Employing sulfuric acid as reactant {1} |
| 550 | DF | .~.~.~.~.~> Ammonia from waste gas |