1. Check if the electrode is damaged;
2, it should be that the time used is too long, first calibrates whether it is effective;
3, can be tried to soak the probe with a KCl solution of 2.5 mmol / L;
4. Clean the glass ball, is it long, and some organic matter is attached, causing the reaction to not be unambiguous;
5, there is a chemical equilibrium ~ CO2 + H2O → H ++ HCO3-, because the general pure water or floor water is weak, the balance is moved in the direction of the reaction, and the pH will continue to rise ~ individual feels Such;
6. Add neutral salts (such as KCl) as an ion intensity modifier, alter the total strength of ions in the solution, increase conductivity, and increase the measurement to be rapidly stable. This method stated in the national standard GB / T6P04.3-93: "When measuring the water sample, a neutral 0.1 mol / lkcl solution is added to the liquid-free water sample when measuring the water sample." Although this method is added. " The ionic strength in the water is changed, causing its pH to change to a certain extent, but experimentally proved that this change only changes from about 0.01 i, it is fully acceptable. However, when using this method, be sure to pay attention to the added KCl solution should not contain any alkaline or acidic impurities. Therefore, the KCl reagent should be highly purity, and the water quality of the solution is also highly purity;
7. At the time of measurement, absorb CO2, pH continues to rise;
8, pH measuring pH, the principle is that the electrode indicating the electrode and the reference electrode is inserted into the solution to form a primary battery, and each unit is equivalent to a 59.1mv of electromotive change per unit at room temperature (25 ° C). The instrument is directly represented by the PH reading, and the temperature difference has a compensation device on the instrument. Since the ions of pure water are small, a stable primary battery cannot be formed, so that neutral salts (such as KCl) are added to the water sample as an ion intensity modifier, and the total strength of the ion in the solution is changed, and the conductivity is increased, and the measurement is increased. Quick and stable;
9, the pH read number is unstable: the solution is determined by the cushioning torch with pH = 4, and the measuring solution is a cushioning rate of pH = 9 with pH = 9. The better the pH of the knocking rate, the better the pH of the measured solution;
10, may be poor contact;
11. I feel that if the pH is slightly shake, the reading will change;
12, should not be the reason of the electrode, I think your electrode is dry, you look at it, the general electrode has a small hole above, and it should be installed in 3mol / LKCl;
13, the electrode is unstable during use, and there is no relationship with the correction, it is related to the power supply voltage fluctuation, the electrode performance, the contact of the electrode, the temperature of the electrode jack, the temperature of the measurement solution. At the time of calibration, if the solution is determined close to the acidity, it is positioned with "6", and if it is alkaline, it is positioned. Both cannot be arbitrarily selected;
14, should be the problem of electrodes, first activation before use. And, the electrode is eliminated for a year, no matter whether it is used. The species of acidic solution was measured, corrected with a buffer liquid near 4 and 7; measuring the matrixic solution, the cushioning of 7 and 10 was applied;
15, pure water's pH is straight to the pH measuring, first use to figure out the measurement principle of the pH meter: It is to display the reading, pure water in the action of the ion contained in the water. The ion is too small, the electrolysis rate is low, how to measure the stability;
16, may be poor contact. Alternatively, the electrode immersion liquid (KCl solution of 3 mol / L) is less, and the electrode is not completely soaked in the electrode soaking solution. There is also an electrode aging, or there should be changed;
17, I want to be related to room temperature, the temperature is low, or the air flow is fast, it will affect the pH meter, keep the room temperature stable, and the doors and windows should be cleared during the time;
18, if the purified water is normal, the unstable is normal, the ion containing is less, the buffering ability is weak, the environment is very large, and the relative stable value is usually taken.
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