| 423 / | HD | CHEMISTRY OF INORGANIC COMPOUNDS |
| 210 | DF | MODIFYING OR REMOVING COMPONENT OF NORMALLY GASEOUS MIXTURE {11} |
| 242.1 | DF | .~ Sulfur or sulfur containing component {3} |
| 243.01 | DF | .~.~ Utilizing aqueous reactant to remove or modify sulfur or sulfur containing component {7} |
| 243.08 | DF | .~.~.~ Alkali or alkali earth compound reactant {2} |
| 243.09 | | .~.~.~.~ Sulfite |