Laboratory instruments: steps and precautions for use of acidity meter （= PH meter)

If you do not pay attention to some precautions during the use of the acidity meter (= PH meter ), it will easily affect the test results. In severe cases, it may cause an input short circuit. The most serious result will be damage to the instrument. No one wants such a result to happen, so before use And pay attention to the way of use during and even after use. Let’s learn how to use the acidity meter safely and effectively.

1. Pay attention when calibrating the calibration solution
2. When measuring the acidity meter, the instrument should be calibrated according to the time period specified in the manual.
3. When calibrating, you should pay attention to:
   The temperature of the scale buffer solution should be as close as possible to the temperature of the measured solution. The positioning scale buffer solution should be as close as possible to the pH value of the solution to be measured. Or two-point calibration, try to make the pH value of the measured solution within the range of the two scale buffer solutions.
   After the acidity meter is calibrated, the electrode immersed in the standard buffer solution should be specially rinsed with water. Due to the buffering effect of the buffer solution, it will cause measurement errors after being brought into the measured solution.
4. When recording the pH value of the measured solution, the temperature value of the measured solution should be recorded at the same time, because the pH value is almost meaningless without the temperature value. Although most pH meters have a temperature compensation function, it only compensates the response of the electrode, that is to say, it is only half-compensated, and does not perform temperature compensation on the measured solution at the same time, that is, full compensation.
5. Pay attention to the use of the electrode of the acidity meter
6. New electrodes or electrodes that have not been used for a long time must be soaked in distilled water for several hours before use. Make the electrode bifurcated and asymmetrically reduce the potential to achieve stability and reduce the internal resistance of the electrode.
7. When using, the internal reference electrode should be
8. When measuring, the electrode bulb should be completely immersed in the solution to be measured.
9. The glass electrode socket should be kept dry and clean. It is strictly forbidden to contact harmful gases such as acid mist and salt mist, and it is strictly forbidden to be stained with aqueous solution to ensure the high input impedance of the instrument.
10. When not measuring, the input should be short-circuited to avoid damage to the instrument.
11. When using the acidity meter, remove the rubber plug of the electrolyte filling port of the reference electrode, so that the reference electrolyte (salt bridge) can seep out at a certain flow rate by gravity and communicate with the measured solution. Otherwise, readings will drift.
12. There should be no air bubbles in the solution, so as not to disconnect the measurement circuit.
13. The salt bridge solution should be added frequently to keep the liquid level higher than the silver/silver chloride wire. Soak in the internal reference solution, do not let the internal reference solution pour to the end of the electrode cap, and make the internal reference suspended.