Determining the pH value of seawater by potentiometric method (CAT#: STEM-ACT-0003-LJX)

The basic principle of pH determination by potentiometric method is based on the law of electromotive force and pH of galvanic cell composed of aqueous solution and electrode. That is, at 25 ° C, whenever the electromotive force of the battery changes by 0.059V, the pH changes by 1 unit. The pH meter mainly includes two parts: electrode and measuring meter (potentiometer). There are two electrodes in the determination: one electrode is used as the comparison standard in the determination, which is the reference electrode, and it should have a stable known potential; The potential of the other electrode changes with the concentration of hydrogen ions in the solution, which is called the indicator electrode. The reference electrodes are calomel electrode, silver chloride electrode and so on. The indicating electrodes are glass electrode, hydroquinone electrode and antimony electrode. The most commonly used are calomel electrodes and glass electrodes.

Used to determine the PH of substances in experiment and production process.

1. Select the "pH" file of the instrument, immerse the cleaned electrode into the standard pH buffer solution to be measured, press the measurement button, turn the positioning adjustment knob, so that the pH value displayed by the instrument is stable in the pH value of the standard buffer solution;
2. Loosen the measuring button, take out the electrode, rinse with distilled water several times, and carefully blot the solution on the electrode with filter paper;
3. Place the electrode in the liquid to be tested, press the measurement button, read the stable pH value, and record. Release the measurement button, remove the electrode, clean it according to step 2, and proceed to the next sample solution measurement. After measuring, clean the electrode and soak the glass electrode in distilled water.

• Sample Type:
Seawater

The sensitive film of the glass electrode is very thin and easy to be broken and damaged. Therefore, when using, be careful not to make the sensitive film collide with hard objects, and the water attached to the electrode can only be gently sucked dry with filter paper, and cannot be wiped.