Refillable glass pH electrodes contain liquid electrolyte solution, which serves to close the electrical circuit in a pH electrode. The electrolyte solution must have electrical contact with the solution being measured. Contact is made via a semipermeable junction, which permits a consistent outflow of liquid electrolyte. Over time, electrolyte is depleted and should be replaced.
- 3.5 M liquid KCl for Sensorex model pH3000