| 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} |
| 244.01 | DF | .~.~ Utilizing solid reactant or catalyst to remove or modify sulfur or sulfur containing component {5} |
| 244.07 | DF | .~.~.~ Alkali or alkaline earth or compound reactant {1} |
| 244.08 | | .~.~.~.~ Carbonate |