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How To Maintain Acidimeter
- Feb 23, 2019 -

1. Storage of pH Glass Electrode

Short term: stored in buffer solution with pH=4;

Long-term: Stored in buffer solution with pH=7.

2. Cleaning of pH Glass Electrode

Contamination of glass electrode bulbs may prolong the electrode response time. CCl4 or soap can be used to wipe off the dirt, and then immersed in distilled water for a day and night to continue to use. When the pollution is serious, it can be soaked in 5% HF solution for 10-20 minutes, washed with water immediately, and then immersed in 0.1N HCl solution for one day and night.

3. Treatment of Aging of Glass Electrode

The aging of glass electrode is related to the gradual change of adhesive layer structure. The old electrode has slow response, high film resistance and low slope. The performance of electrodes can often be improved by etching the outer layer with hydrofluoric acid. If this method can be used to remove the inner and outer layer of the adhesive layer periodically, the life of the electrode is almost infinite.

4. Storage of reference electrodes

The best storage solution for Ag-AgCl electrode is saturated potassium chloride solution. High concentration potassium chloride solution can prevent silver chloride from precipitating at the liquid junction and maintain the liquid junction in working state. This method is also suitable for the storage of composite electrodes.


Most of the problems of reference electrodes are caused by the blockage of liquid junction, which can be solved by the following methods:

(1) The interface of immersion solution: 10% saturated potassium chloride solution and 90% distilled water mixture were heated to 60-70 C, and the electrode was immersed in about 5 cm for 20 minutes to 1 hour. This method can dissolve the crystallization at the end of the electrode.

(2) Ammonia immersion: When the liquid junction is blocked by silver chloride, it can be removed by concentrated ammonia water. The specific method is to fill and wash the electrode, and immerse the liquid in ammonia water for 10 to 20 minutes after emptying, but do not let the ammonia water into the electrode. Remove the electrode and wash it with distilled water. Re-add the inner filling solution and continue to use.

(3) Vacuum method: the hose is wrapped around the reference electrode liquid junction, and the water flow suction pump is used to fill the suction part through the liquid junction to remove the mechanical blockage.

(4) Boiling liquid boundary: The liquid boundary of Ag-AgCl reference electrode is immersed in boiling water for 10-20 seconds. Note that the electrode should be cooled to room temperature before the next boiling.

(5) When the above methods are invalid, the mechanical method of sandpaper grinding can be used to remove blockage. This method may cause abrasive grains to plug into the liquid interface. Cause permanent blockage.