Introduction to pH meter composite electrode
The electrode that combines a pH glass electrode with a reference electrode is called a pH composite electrode. A plastic shell pH composite electrode is called a plastic shell electrode. A glass pH composite electrode is called one with a glass shell. The biggest advantage of composite electrodes is that they are combined into one and easy to use. The structure of pH composite electrode mainly consists of electrode bulb, glass support rod, internal reference electrode, internal reference solution, shell, external reference electrode, external reference solution, liquid interface, electrode cap, electrode wire, socket, etc.
1. Electrode bulb: It is made by melting and blowing lithium glass with hydrogen function, in a spherical shape, with a film thickness of about 0.1-0.2mm, and a resistance value of 250 megaohms (25 ℃).
2. Glass support tube: It is a glass tube body that supports electrode bubbles, made of lead glass with excellent electrical insulation properties, and its expansion coefficient should be consistent with that of electrode bubble glass.
3. Internal reference electrode: It is a silver/silver chloride electrode, mainly used to extract electrode potential, requiring stable potential and small temperature coefficient.
4. Internal reference solution: An internal reference solution with a zero potential of 7pH, which is a mixed solution of neutral phosphate and potassium chloride. The pH value at which the glass electrode and reference electrode form the battery to establish a zero potential mainly depends on the pH value and chloride ion concentration of the internal reference solution.
5. Electrode plastic shell: The electrode plastic shell is a shell that supports glass electrodes and liquid interfaces, and contains external reference solutions. It is formed by PPS plastic compression molding.
6. External reference electrode: It is a silver/silver chloride electrode that provides and maintains a fixed reference potential, requiring stable potential, good reproducibility, and a small temperature coefficient.
7. External reference solution: 3.3mol/L potassium chloride gel electrolyte, not easy to lose, no need to add.
8. Sand core liquid interface: The liquid interface is a connecting component that connects the external reference solution and the measured solution, requiring stable permeability.
9. Electrode wire: It is a low-noise metal shielded wire, with the inner core connected to the inner reference electrode and the shielding layer connected to the outer reference electrode.
