Under what circumstances should the supporting pH glass electrode of the pH meter be cleaned and maintained
1. Under what circumstances should the pH glass electrode be cleaned?
Put the pH glass electrode and the reference electrode into the standard buffer solution of pH 7.00, when the reference electrode uses a calomel electrode, the millivolt reading should be 0+/-30 millivolts; use the Ag/AgCl electrode as the reference electrode , the reading should be 0+/-80 mV;
Put it into the buffer solution of pH 4.00, the reading should be >160 millivolts; when the glass electrode is used as the indicating electrode and the calomel electrode is used as the reference electrode, the change of the pH value of 1 unit at 25 degrees Celsius, the change of the potential difference is 59 millivolt. If the reading does not match the above range, it should be cleaned;
After measuring a certain solution, wash it carefully and dry the water drops before measuring the next sample; measure oily samples, especially those with oil slicks, clean them with CCI4 or acetone after use, and then use 1.2mol Rinse with /L hydrochloric acid, then rinse with distilled water, soak in distilled water to balance for a day and night before use; after measuring the turbid solution, rinse it with distilled water in time; after measuring the emulsified solution, clean the electrode with detergent and distilled water in time, and then soak In distilled water; there should be no air bubbles between the inner electrode of the glass electrode and the bulb. If there are air bubbles, you can lightly shake them to let the air bubbles escape.
When using a new pH meter electrode, it needs to be adjusted and soaked in distilled water for a period of time to form a good hydration layer; the soaking time is related to the composition of the glass and the thickness of the film. Generally, the soaking time of new electrodes and electrodes with low glass conductivity and thicker films It is advisable to take 24 hours; otherwise, the soaking time can be shorter. The instructions indicate that the electrodes that are used for the first time or have not been used for a long time need only be soaked in 3N KCL solution or deionized water for 2-10 hours;
2. Under what circumstances should the pH glass electrode be maintained?
If there is oil on the electrode, it can be wiped lightly with cotton soaked in CCl4 or acetone. Then put it in 0.1mol/L HCI solution for 12 hours, and then rinse it repeatedly with distilled water; how to maintain it? The commonly used pH electrode can be placed in a pH4.00 buffer solution or soaked in distilled water for a short period of time. For long-term storage, use PH7.00 buffer solution or put it in a box with a rubber cap.
