pH meter electrodes measure the degree of acidity by comparing the aqueous solutions. The electrodes are immersed in with the reference half-cells built inside the electrodes. These half-cells are coated with silver chloride or AgCl.
With AgCl inside the electrode and KCl outside the electrode, a concentration gradient develops between the two aqueous environments over the difference in the concentration of hydrogen ions. This leads to a development of potential difference that can be measured in millivolts, that is used to measure the pH in turn.
In addition to pH, the electrode can also convert the millivolts signal into a temperature sensor, as the temperature can affect the pH calibration of the electrode. Most modern pH meter electrode has an in-built temperature sensor that detects the temperature automatically.
pH calibration buffers like KCl are standardized solutions of fixed pH values that are calibrated up to an accuracy of 0.001 pH. These buffer solutions are certified for quality control after calibrating twice or even thrice to assure of its reliability, even though calibrating the buffer solution once with a pH reference buffer is typically sufficient to guarantee the ability and accuracy of the pH calibration buffer in measuring a range of pH values.
Related: Working Principle of pH Meter
However, before the electrode is soaked in KCl, it needs to be washed with distilled water. This stage of washing the electrode has to be quick as prolonged exposure of the pH meter electrode to distilled water can compromise with its ability to effectively measure the pH, by damaging the special glass membrane that contains the reference half-cells.
Other factors that can threaten the effectiveness of the pH meter electrode include the entry of KCl into the glass bulb of the electrode, which should be prevented by the diaphragm that forms a protective barrier between the glass bulb and the surrounding KCl solution.
With AgCl inside the electrode and KCl outside the electrode, a concentration gradient develops between the two aqueous environments over the difference in the concentration of hydrogen ions. This leads to a development of potential difference that can be measured in millivolts, that is used to measure the pH in turn.In addition to pH, the electrode can also convert the millivolts signal into a temperature sensor, as the temperature can affect the pH calibration of the electrode. Most modern pH meter electrode has an in-built temperature sensor that detects the temperature automatically.
pH calibration buffers like KCl are standardized solutions of fixed pH values that are calibrated up to an accuracy of 0.001 pH. These buffer solutions are certified for quality control after calibrating twice or even thrice to assure of its reliability, even though calibrating the buffer solution once with a pH reference buffer is typically sufficient to guarantee the ability and accuracy of the pH calibration buffer in measuring a range of pH values.
Related: Working Principle of pH Meter
However, before the electrode is soaked in KCl, it needs to be washed with distilled water. This stage of washing the electrode has to be quick as prolonged exposure of the pH meter electrode to distilled water can compromise with its ability to effectively measure the pH, by damaging the special glass membrane that contains the reference half-cells.
Other factors that can threaten the effectiveness of the pH meter electrode include the entry of KCl into the glass bulb of the electrode, which should be prevented by the diaphragm that forms a protective barrier between the glass bulb and the surrounding KCl solution.
Very helpful information.
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