How to use the acidity meter
The acidity meter is referred to as a pH meter, which consists of two parts: an electrode and an electric meter. If the electrodes can be maintained reasonably, the standard buffer solution can be prepared according to the requirements, and the electrometer can be operated correctly during use, the error of pH indication can be greatly reduced, thereby improving the reliability of chemical experiments and medical inspection data.
1. How to use the acidity meter correctly and maintain the electrodes
At present, the electrodes used in laboratory acidity meters are all composite electrodes, which have the advantages of being easy to use, not affected by oxidizing or reducing substances, and having a fast equilibrium speed. When in use, remove the rubber sleeve on the electrode filling port and the rubber sleeve at the lower end to maintain the hydraulic pressure difference of the potassium chloride solution in the electrode. The following is a brief introduction to the use and maintenance of electrodes:
1. When the composite electrode is not in use, it can be fully soaked in 3M potassium chloride solution. Do not soak with washing liquid or other water-absorbing agents.
2. Before use, check the bulb at the front end of the glass electrode. Under normal circumstances, the electrode should be transparent without cracks; the bulb should be filled with solution without air bubbles.
3. When measuring a solution with a high concentration, shorten the measurement time as much as possible, and wash it carefully after use to prevent the measured liquid from adhering to the electrode and polluting the electrode.
4. After cleaning the electrodes, do not wipe the glass membrane with filter paper, but dry it with filter paper to avoid damage to the glass membrane, prevent cross-contamination, and affect measurement accuracy.
5. During the measurement, pay attention to the silver-silver chloride internal reference electrode of the electrode should be immersed in the chloride buffer solution in the bulb to avoid the digital jumping phenomenon in the display part of the electric meter. When using, pay attention to gently shake the electrode a few times.
6. The electrode cannot be used in strong acid, strong alkali or other corrosive solutions.
7. It is strictly forbidden to use in dehydrating medium such as absolute ethanol, potassium dichromate, etc.
2. How to use the acidity meter Preparation and storage of standard buffer solution
1. The pH standard substance should be stored in a dry place. For example, the mixed phosphate pH standard substance will deliquesce when the air humidity is high. Once deliquescence occurs, the pH standard substance cannot be used.
2. Secondary distilled water or deionized water should be used to prepare pH standard solution. If it is used for 0.1 grade pH meter measurement, ordinary distilled water can be used.
⒊The prepared pH standard solution should be diluted with a smaller beaker to reduce the pH standard solution sticking to the beaker wall. In addition to emptying the plastic bags or other containers that store pH standard substances, they should also be rinsed with distilled water several times, and then poured into the prepared pH standard solution to ensure that the prepared pH standard solution is accurate.
4. The prepared standard buffer solution can generally be stored for 2-3 months. If turbidity, mold or precipitation are found, it cannot be used any longer.
5. Alkaline standard solution should be sealed and stored in polyethylene bottles. Prevent carbon dioxide from forming carbonic acid after entering the standard solution and lower its pH value.
3. Correct calibration of pH meter
There are many types of pH meters due to the different designs of the electric meters, and their operating steps are different. Therefore, the operation of the pH meter should be carried out strictly in accordance with its instruction manual. In specific operations, calibration is an important step in the operation of pH meters. The data in Table 1 are the measured values of the uncalibrated and calibrated pH meters with an accuracy of 0.01 grade and passed the metrological verification, from which we can see the importance of calibration.
