Introduction:PH meterRegular calibration is required to ensure that the test results are accurate.

PH meterRegular calibration is required to ensure that the test results are accurate. So how to calibrate the pH meter?

Generally, the following three solutions are used:
1. Potassium hydrogen phthalate (KHC8H4O4) 4.003PH;
2. Mixed phosphate basin (Na2HPO4) pH 6.864;
3. Borax (Na2B4O7 · l0H2O) 9.182 pH (at 25 ℃). Clean the electrode with distilled water at constant temperature, and fill a beaker with distilled water to soak the electrode part, so that the residual impurities in the electrode part are fully dissolved.

Calibration steps:

1. Adjust the slope of the instrument to the maximum and open the rubber stopper on the upper part of the electrode to expose the small hole. Otherwise, negative pressure will be generated during calibration, causing the solution to not perform ion exchange properly and resulting in inaccurate measurement data.

2. Remove the electrode from the beaker containing distilled water and use filter paper to absorb any remaining distilled water on the electrode.

3. Place the electrode into a beaker containing a mixed phosphoric acid basin and wait for at least 15 minutes.

4. Adjust the positioning knob on the instrument to display 6.86pH, and first set the reference point for the instrument.

5. Take out the electrode from the beaker containing the mixed phosphoric acid for 1 hour, wash the electrode with distilled water, and place it in the beaker containing distilled water. Wait for about 3 minutes to dissolve the residual part of the mixed phosphoric acid for 1 hour.

6. Remove the electrode from the beaker containing distilled water and use filter paper to absorb any remaining distilled water on the electrode.

7. Place the electrode in a solution containing potassium hydrogen phthalate or borax, wait for more than 15 minutes, and observe whether the instrument displays a pH of 4.00 or 9.18. If not, adjust the slope knob on the instrument to display a pH of 4.00 or 9.18, which is a commonly used two-point calibration.

8. If three-point calibration is required, simply repeat the same steps for the other solution.

When using a pH meter, avoid:
Contact with humid gases, hard objects, oil stains, foaming and crystallization of potassium chloride solution, long-term non replacement of glass electrodes, etc.

Proper use of a pH meter can prolong the lifespan of the instrument.