Sodium- and Sulfur-Activity Measurements Using Glass-Membrane Reference Electrodes/Sensors

摘要

Development of miniature reference electrode systems and designs to measure either sodium or sodium polysulfide activity has continued. The reference electrodes use small (2-mm sup 2 active area), thin membranes of a highly Na sup + -ion-conductive glass. Stable, reproducible emf measurements which reflect activity differences have been observed from (Mo)Na vertical bar Glass vertical bar Na sub 2 S sub 4 (Mo) and Na sub 2 S/sub x/(Mo) vertical bar Glass vertical bar Na sub 2 S/sub y/(Mo) (x = 3, 4, and 5) cells at elevated temperatures. The utility of the electrode design was demonstrated by performing coulometric titrations of polysulfide electrodes (ca. 2-mAh capacity to Na sub 2 S sub 3 ) in the temperature range of 300 to 400 sup 0 C. The coulometric titrations clearly show a sharp transition from the two-phase region to a single phase at 71 mol % sulfur. The lowest demonstrated temperature of operation for the reference electrode is 123 sup 0 C in NaCl/AlCl sub 3 melts. (ERA citation 12:045520)