bThe electrochemical couple thus formed results in a constant potential according to the Nernst equation. The inner solution of a reference electrode makes contact with the solution of which the electrical potential has to be measured by means of a barrier, the so-called frit. Often glass membrane electrodes are combined with reference electrodes to one system.
Various performances of such rather bulky electrode assemblies, both separate pH glass electrodes and reference electrodes, as well as combined systems, are in daily use in laboratories of chemical analysis, process industry etc. A typical performance of a combined pH glass electrode is shown in figure 1.