What are the main structures of the pH meter composite electrode?
1. Electrode bulb: It is made of molten lithium glass with hydrogen function and is spherical in shape, with a film thickness of about 0.1-0.2mm and a resistance value of <250 megohms (25°C).
2. Glass support tube: it is the glass tube that supports the electrode bulb. It is made of lead glass with excellent electrical insulation. Its expansion coefficient should be consistent with that of the electrode bulb glass.
3. Internal reference electrode: silver/silver chloride electrode, the main function is to lead out the electrode potential, which requires stable potential and small temperature coefficient.
4. Internal reference solution: The internal reference solution with a zero potential of 7pH is a mixed solution of neutral phosphate and potassium luide. The glass electrode and the reference electrode form a battery to establish the pH value of the zero potential, which mainly depends on the internal reference solution. pH value and chloride ion concentration.
5. Electrode molded case: The electrode molded case is a shell that supports the glass electrode and the liquid junction, and holds the external reference solution, and is molded by PPS.
6. External reference electrode: silver/silver chloride electrode, the function is to provide and maintain a fixed reference potential, which requires stable potential, good reproducibility and small temperature coefficient.
7. External reference solution: 3.3 mol/L potassium sulfide gel electrolyte, which is not easy to lose and does not need to be added.
8. Sand core liquid junction: The liquid junction is the connecting part that connects the external reference solution and the measured solution, and requires stable penetration.
9. Electrode wire: It is a low-noise metal shielded wire, the inner core is connected to the inner reference electrode, and the shielding layer is connected to the outer reference electrode.
