| 204 / | HD | CHEMISTRY: ELECTRICAL AND WAVE ENERGY |
| 193 | DF | APPARATUS {5} |
| 194 | DF | .~ Electrolytic {11} |
| 400 | DF | .~.~ Analysis and testing {20} |
| 416 | DF | .~.~.~ Ion-sensitive electrode {3} |
| 419 | | .~.~.~.~ Inorganic membrane {1} |
| 420 | DF | .~.~.~.~.~> Glass ion-selective membrane |