pH meter | acidity meter debugging introduction
The commonly used pH and acidity meters in the laboratory include the old-fashioned domestically produced Leici 25 type acidity meter with a minimum division of 0.1 units and the pHS-2 type pH and acidity meter with a minimum division of 0.02 units. The pH value of these pH and acidity meters is displayed by the pointer of the electric meter. The new digital pH meter | acidity meter has the KL series from domestic company Kelilon, and its set temperature and pH value are displayed in digital form on the screen. Regardless of the pH meter or acidity meter, it is necessary to perform secondary calibration with standard buffer solution before use.
Firstly, read the instrument manual, connect the power supply, and install the electrodes. Add a standard buffer solution with a pH value of 7.0 to a small beaker, immerse the electrode, gently shake the beaker to make the solution in contact with the electrode uniform. Read the pH value of the solution according to the instructions provided with different pH and acidity meters, calibrate the pH and acidity meters to ensure that their readings are consistent and stable with the actual value of pH 7.0 in the standard buffer solution; Then remove the electrode from the solution and rinse thoroughly with distilled water. Transfer the small beaker to a standard buffer solution with pH 4.01 or 0.01, immerse the electrode, and repeat the above steps to stabilize the reading. This completes the second key point correction; After calibration, rinse the electrode and beaker with distilled water. After calibration, do not rotate the positioning adjuster again, otherwise it must be recalibrated.
Maintenance of pH meter
Glass electrodes must be soaked in distilled water for at least one day and night before initial use, and should also be soaked in distilled water for ready use at any time. Glass electrodes should not be in contact with strong water absorbing solvents for too long. When used in strong alkaline solutions, they should be operated as soon as possible. After use, they should be washed immediately with water. The bubble film of glass electrode balls is very thin and should not come into contact with glass cups or hard objects; When the glass film is stained with oil, it should be soaked in alcohol first, then carbon tetrachloride or ether, and finally soaked in alcohol before being washed with distilled water. When measuring the pH of a protein containing solution, if the electrode surface is contaminated with proteins, resulting in unreliable and unstable readings and errors, the electrode can be soaked in dilute HCl (0.1mol/L) for 4-6 minutes to correct. After cleaning the electrode, only gently dry it with filter paper. Do not wipe it with fabric, as this can cause static charges on the electrode and result in incorrect readings. When using calomel electrodes, it is important to fill the electrode with potassium chloride solution and ensure that there are no bubbles to prevent disconnection. There should be a small amount of potassium chloride crystals present to keep the solution saturated. When using, remove the rubber stopper at the top of the electrode and let a small amount of potassium chloride solution flow out from the capillary tube to ensure reliable measurement results.
