P/R65 Page 8
4. Brush the end of the probe, particularly the three electrodes with a soft bristle brush such as a
toothbrush. Take care not to scratch the glass electrode.
5. If the probe is still not clean, it may have to be cleaned with acid. CAUTION: Do not acid clean
probes used in processes containing cyanide solutions. Some experimentation may be required to
determine the most suitable acid for your process. Use the most dilute acid, which is effective.
Normally 10 parts of water to one part muriatic acid is sufficient. Do not use hydrofluoric acid.
6. Soak the probe for not more than 5 minutes in the chosen acid; then rinse thoroughly with clean
warm water and soak in water for 3-5 minutes.
Calibrate the system in accordance with the instrument instruction manual.
4.2. Replacement of Salt Bridge for Series 4, 5, 6, 7 & S Differential Probes
1. If the system cannot be calibrated after cleaning the probe, it may be necessary to replace the
standard cell solution. A kit is available from Water Analytics for this purpose (Part No. C35-17K).
Proceed as follows: Refer to DWG N106-60.
2. Hold the probe vertically with the sensor face up. Insert long nose pliers in the blind holes in the salt
bridge and turn counter-clockwise taking care not to damage the glass electrode. Discard the used
salt bridge.
3. Up-end the probe and pour out the contents of the standard electrode chamber. Flush the chamber
with a small amount of pH 7 buffer or clean water.
4. Refill the chamber with 7pH buffer solution up to the tip of the electrode inside the chamber. DO
NOT OVERFILL. It is important to leave space for the salt bridge thread and a small amount of air.
5. Screw the new salt bridge into the cavity until finger tight. Now turn 1/4 turn with long nose pliers.
The front face of the salt bridge should be flush with the probe face.
4.3. Replacement of Salt Bridge for Series 8 Differential Probes
1. If the system can’t be calibrated after cleaning the probe, it may be necessary to replace the
standard cell solution and/or the salt bridge. A salt bridge kit is available from Water Analytics for
this purpose (Part No. AM60-9765K for the -8 probe and C35-17K for the -5, -6 and -7 probes).
Proceed as follows: Refer to DWG N106-60.
2. Hold the probe vertically electrodes up. Remove the used salt bridge. For the -8 probe the salt
bridge is a hexagonal-shaped capsule that can be removed using a 9/16” socket wrench. For the -
5, -6 and -7 probes the salt bridge is a round capsule that is flush with the probe front. Use needle
nose pliers to unscrew the piece.
3. Discard the used salt bridge.
4. Dispose of the used solution inside the bridge chamber and flush with pH 7 solution or distilled
water.
5. Refill the chamber with 7pH buffer solution, up to the tip of the electrode, inside the chamber. DO
NOT OVERFILL. It is important to leave space for the salt bridge thread and a small amount of air.
6. Screw the new salt bridge into the cavity until finger tight. Now perform a 1/4 turn with a 9/16”
socket wrench. The salt bridge edges should be flush with the front of the probe face.
