Potassium chloride solution for redox and pH combination electrodes
€9.45*
Available, delivery time: 1-4 days
For refilling and storing standard redox and pH combination electrodes (3 molar) or special pH combination electrodes for low-ion water (4 molar - only if the instructions or the manufacturer expressly specify this concentration!)
Not for refilling gel electrodes!
Gel electrodes cannot be maintained and are therefore not really suitable for aquaristic purposes (continuous measurement!). If they can no longer be calibrated or if they only reach the measured value extremely slowly, they have reached the end of their service life and must be replaced with a new one.
You can try to extend the service life of these electrodes by regularly adjusting them in potassium chloride solution. However, if the electrodes are already behaving rather sluggishly, this measure must be repeated at ever shorter intervals in order to achieve a usable response behaviour.
It should be mentioned that a particularly fast response is not normally necessary for continuous measurements, as the pH-based control of the CO2-content is a very slow process anyway and therefore a few minutes more or less are not important.
The function of all other measuring chains can be greatly supported by topping up or replacing the potassium chloride electrolyte.
Normally and in the vast majority of cases, 3 molar solutions are used, but special electrodes with 4 molar or saturated electrolyte may also be available on the market for ion-poor media.
| 3 molar | 22.37 g potassium chloride (KCl) / 100 ml solution |
| 4 molar | 29.82 g potassium chloride (KCl) / 100 ml solution |
| Saturated (at 20 °C: 4.61 molal) | 34.40 g potassium chloride (KCl) / 100 g water |
We only use potassium chloride in p.a. quality for the production of KCl solutions.
Cleaning
Electrodes in continuous operation in the aquarium tend to develop a biological "lawn" (biofilm) over time. A bacterial layer forms which makes the measurement sluggish and falsifies it, in the worst case the electrodes even become algalised.
To remove protein-containing deposits, cleaning solutions have been developed that are modelled on the contents of our stomach. They contain pepsin and 0.1 molar hydrochloric acid (pH ~ 1) and are good at removing proteins resulting from the decomposition of protein-containing substances in the aquarium. However, many bacteria and algae survive even this treatment relatively unscathed.
In our experience, there is an inexpensive and effective alternative that does not harm the electrode when used for a short time and has been proven to kill and remove bacteria and algae.
The electrode is placed in a 6 % hydrogen peroxide solution for 15 minutes. It is sufficient to repeat this treatment every 4 - 6 weeks.
The last resort for electrodes that hardly react at all is a regeneration test with diluted hydrofluoric acid or ammonium bifluoride solution. However, this treatment should be reserved for specialists, not only because incorrect or inexpert use can cause more damage than good to the pH electrode, but also because burns with hydrofluoric acid (even diluted hydrofluoric acid) are among the worst injuries that can be inflicted when using chemicals! The tissue is destroyed by precipitation of the vital calcium. Such wounds are very deep and take a long time to treat and heal. The first antidote when working with hydrofluoric acid should at least be a container with a solution of a calcium salt (works by forming sparingly soluble CaF = fluorspar)! Salts with organic anions, such as calcium gluconate, which are easily absorbed by the tissue, are best suited for this purpose.
Further information
Read a detailed, in-depth article by Klaus Haber on the principles of pH measurement and the structure, function and maintenance of electrodes.
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13 February 2025 00:00
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