Introduction of three electrodes of pH meter
What is a pH indicating electrode?
The electrode that responds to the activity of hydrogen ions in the solution and the electrode potential changes accordingly is called a pH indicating electrode or a pH measuring electrode. There are several kinds of pH indicating electrodes, such as hydrogen electrode, antimony electrode and glass electrode, but the most commonly used one is glass electrode. The glass electrode is composed of a glass strut and a hydrogen ion-sensitive glass membrane composed of a special composition. The glass membrane is generally in the shape of a bulb. The bulb is filled with an internal reference solution, inserted into an internal reference electrode (usually silver/silver chloride electrode), sealed with an electrode cap to lead out wires, and fitted with a socket to become a pH indicator. electrode. A single pH indicating electrode cannot be measured, it must be measured together with a reference electrode.
2. What is a reference electrode?
An electrode that does not respond to the activity of hydrogen ions in solution and has a known and constant electrode potential is called a reference electrode. There are several reference electrodes such as mercurous sulfate electrode, calomel electrode and silver/silver chloride electrode. The most commonly used are calomel electrodes and silver/silver chloride electrodes. The role of the reference electrode in the measurement battery is to provide and maintain a fixed reference potential. Therefore, the requirements for the reference electrode are stable and reproducible potential, small temperature coefficient, and small polarization potential when current passes.
3. What is a pH composite electrode?
An electrode that combines a pH glass electrode and a reference electrode is called a pH composite electrode. The case with plastic shell is called plastic shell pH composite electrode. The one with glass shell is called glass pH composite electrode. The biggest advantage of the composite electrode is that it combines two into one and is easy to use. The structure of pH compound electrode is mainly composed of electrode bulb, glass support rod, internal reference electrode, internal reference solution, shell, external reference electrode, external reference solution, liquid junction, electrode cap, electrode wire, socket and so on.
