Problems related to acidity meter
1. How to treat temperature compensation? Can temperature compensation remove temperature-induced pH measurement errors?
Strictly speaking, temperature compensation should include three parts: temperature compensation of electrode slope, solution temperature compensation, temperature compensation of electrode zero point (including measuring electrode and reference electrode). The temperature compensation set on the pH meter is only the slope item of the compensation electrode (2.303RT/F). Therefore, temperature compensation is not very sufficient for pH meter measurement, nor can it completely eliminate the error caused by temperature. Only because the temperature item of the solution and the zero-degree temperature item of the electrode can not be determined, and the error caused by it is very small, so it is omitted!
2. How to check the quality of the pH meter?
Generally, the quality of the electrode is mainly judged by the slope of the electrode, and it can also be judged by the zero mV value of the electrode.
For electrodes in industrial occasions, the factory standard is a slope of 95%--105%. Zero potential: ±15mV, zero potential is a range, within this range are very good electrodes, not 8.2mV given by some meter manufacturers, limit the zero potential of electrodes to around 8.2mV. After a period of use, the zero potential will change, and within ±60 mV is not allowed. However, the slope should not be lower than 70%, and if higher is required, it should not be lower than 80%.
3. Why must the pH electrode be soaked before use?
The pH electrode must be soaked before use, because the pH bulb is a special glass membrane, and there is a thin layer of hydrated gel on the surface of the glass membrane. H+ in solution has a stable good response. If the immersion is not sufficient, the response value will be unstable and drift during measurement. The soaking time is generally more than 24 hours.
For pH single glass electrode, it can be soaked in distilled water or 3.0N KCL solution, while single reference electrode can only be soaked in 3.0N KCL solution. For the PH composite electrode, you can use desalted water or distilled water or 3.0N solution, if soaked for a long time, you must use 3.0N KCL solution. When using PH single glass electrodes before, everyone has been used to soaking in ionized water. If using PH composite electrodes, they are still soaked in deionized water for a long time, then this wrong soaking method will make: a pH electrode with good performance becomes Form an electrode with slow response and poor precision, and the longer the immersion time, the worse the performance, because after long immersion, the KCL concentration of the electrode reference system will be greatly reduced, and the liquid junction potential will increase and become unstable.
