| 423 / | HD | CHEMISTRY OF INORGANIC COMPOUNDS |
| 1 | DF | TREATING MIXTURE TO OBTAIN METAL CONTAINING COMPOUND {15} |
| 155 | DF | .~ Alkaline earth metal (Mg, Ca, Sr, or Ba) {11} |
| 170 | DF | .~.~ Treating impure sulfate (e.g., barite, etc.) {1} |
| 171 | | .~.~.~ Calcining gypsum {1} |
| 172 | DF | .~.~.~.~> With steam or at specified temperature |