The electrode which combines the pH glass electrode and the reference electrode is the pH composite electrode. According to the different shell materials, two kinds of plastic shell and glass are divided. The greatest advantage of the composite electrode is that it is convenient to use relative to the two electrodes. The pH composite electrode is mainly composed of electrode glass bulb, support rod, internal reference electrode, the reference solution, an outer reference electrode and the reference solution, liquid junction, electrode cap, electrode wires, socket etc..
(1) electrode bubble: it is made by melting of the lithium glass with hydrogen function. It is spherical, the thickness of the film is about O.1 to 0.2mm, and the resistance value is less than 250 Mega (25).
(2) the glass support tube is a glass tube supporting the electrode ball, which is made of lead glass with excellent electrical insulation, and its expansion coefficient should be the same as that of the electrode bulb.
(3) internal reference electrode: for the silver / silver chloride electrode, the main role is to lead the electrode potential, the potential stability, small temperature coefficient.
(4) the reference solution: zero potential 7pH internal reference solution, is a mixture of neutral phosphate and potassium chloride, glass electrode and a reference electrode battery established zero potential pH value, mainly depends on the internal reference solution pH value and chlorine ion concentration.
(5) electrode shell: electrode shell support glass electrode and the liquid junction, a reference solution shell, usually made of polycarbonate (PC) moulding plastic or glass. PC plastic will dissolve in some solvents, such as carbon tetrachloride, three chloride, tetrahydrofuran, if the test contains more solvent, it will damage the electrode shell, you should switch to glass shell pH composite electrode.
(6) external reference electrode: Silver / silver chloride electrode. The action is to provide and maintain a constant reference potential, requiring stable potential, good reproducibility and small temperature coefficient.
(7) external reference solution: potassium chloride solution or KCl gel electrolyte.
(8): the liquid junction is connected with the liquid junction components reference solution and test solution, requirements shentouliang stability, usually with sand core.
(9): low noise wire electrode metal shielding wire, the inner core and the internal reference electrode connected to the shielding layer and the outer reference electrode connection.