Reference electrode EPBRE

External pressure-balanced reference electrodes (EPBREs) have been developed and evaluated extensively over the past three decades. The first variant was described in 1978 by Macdonald et al. ° and was patented in the same year, with the invention being assigned to the Electric Power Research Institute. The electrode won the EPRI Invention-of-the-Year Award in 1979. The EPBRE that was first evaluated is described thermodynamically as the thermocell ... 

Figure 21. Assembly of an external pressure-balanced reference electrode (EPBRE). Reprinted from Ref. 50, Copyright (1992) with permission from Plenum.

All of the calculations described above correspond to Soret s initial state, i.e., to a state where the concentration of electrolyte along the bridge is constant. As noted above, maintaining the thermal junction in the initial state has been a vital problem in the operation of external pressure balanced reference electrodes. As also noted above, in the original design of the EPBRE (Fig. 21),... 

It is also important to note that the YSZ electrode is a primary pH sensor and hence (in principle) does not require calibrating. However, this is not the case with the EPBRE, which forms the other half of the cell. At the present time, no method exists for calculating the reference electrode potential, a priori, so that calibration is the only comse for devising a practical pH sensor. Calibration requires knowledge of the activity of H and the fugacity... 

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