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The use of pH and acidity meters

2024-01-23 14:44

PH meter | acidity meter debugging

The commonly used pH meters in the laboratory include the old-fashioned domestically produced Thunder Magnetic 25 pH meter with a minimum division of 0.1 units and the pHS-2 pH meter with a minimum division of 0.02 units. The pH value of these pH meters is displayed by the meter pointer.

First, read the instrument user manual, connect the power, and install the electrodes. Add standard buffer solution with a pH 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 attached to different pH meters, calibrate the pH meter, and ensure that its reading is 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 it thoroughly with distilled water. Replace the small beaker with a standard buffer solution of pH 4.01 or 0.01, immerse the electrode, and repeat the above steps to stabilize its reading. This completes the second key correction; After calibration, rinse the electrode and beaker with distilled water. Do not rotate the positioning adjuster after calibration, otherwise it must be recalibrated.

Use of pH meter | Acidity meter

The temperature of the measured solution should be the same as that of the standard buffer solution. Therefore, the temperature regulator or slope adjustment knob must be adjusted before use. Advanced pH meter | Acidity meter has a temperature compensation system installed in the circuit, and the instrument can automatically adjust temperature changes after initial calibration.? When measuring, first rinse the two electrodes with distilled water, gently absorb the residual solution on the electrodes with filter paper, or wash the electrodes with the test solution. Then, immerse the electrode into a beaker containing the solution to be measured, gently shake the beaker to make the solution uniform, press the reading switch, and the value indicated by the pointer is the pH value of the solution to be measured. Repeat several times until the value remains unchanged. When the digital pH meter | acidity meter changes less than 0.01 pH value within about 10 seconds, it indicates that a stable reading has been reached. After the measurement is completed, turn off the power, rinse the electrodes, and soak the glass electrodes in distilled water.

Maintenance of pH meter and acidity meter

Glass electrodes must be soaked in distilled water for at least one day and night before their initial use, and should also be soaked in distilled water for future use. Glass electrodes should not come into contact with strong absorbent solvents for too long. When used in strong alkaline solutions, they should be operated as soon as possible. After use, they should be washed with water immediately. The bubble film of glass electrode balls is very thin and should not touch glass cups or hard objects; When the glass film is stained with oil, it should be soaked in alcohol first, followed by carbon tetrachloride or ethylene glycol, and finally washed with distilled water. If the pH of a solution containing protein is measured and the electrode surface is contaminated with protein, 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 electrodes, only use filter paper to gently dry them, and do not use fabric to wipe them, as this can cause static charges on the electrodes and result in incorrect readings. When using calomel electrodes, pay attention to filling the electrode with potassium chloride solution and ensuring there are no bubbles to prevent circuit breakers. 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 out a small amount of chlorine from the capillary tube

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