What do you know about pH electrodes
The electrode is a part of the pH meter. pH measurement is done through the measuring electrode, reference electrode composed of a chemical cell.
(1) pH measurement electrode is also called pH indicator electrode, the hydrogen ion activity in the solution has a response, the electrode potential changes. Almost all modern pH meters use glass electrodes as the measuring electrode.
(2) Reference electrode (inert electrode), no response to the hydrogen ion activity in the solution. In the pH measurement, it as a constant potential half-cell and pH measurement electrode form a chemical cell, to provide and maintain a fixed reference potential.
(3) Composite electrode is a combination of pH measurement electrode and reference electrode. Composite electrode is not affected by oxidising and reducing substances, balance faster, more widely used, the current pH measurement are basically such electrodes. Whether the glass indicator electrode or glass composite electrode, is a film electrode, the film potential and the measured hydrogen ion activity in the solution is energy-starter relationship, reflecting the unique performance of the film electrode, these properties by the electrode itself and the use of the conditions of the impact, and on the results of the role of the measurement.
The pH (acidity) meter is a potentiometric instrument for determining the activity of H+ in a solution. the value measured by the pH meter is used as a way to indicate the acidity of a solution, which is expressed as the negative logarithm of the concentration of H+ ions in the solution, i.e.: pH = ーlg[H+].
We use the pH meter, are by the meter and electrode two parts. In the actual measurement, the electrode is immersed in the solution to be measured, the concentration of H+ ions in the solution is converted into a millivolt voltage signal, input meter. The meter will amplify the signal, and after logarithmic conversion to pH, and then by the millivolt level display meter shows the pH.
The pH meter uses a glass electrode as the measuring electrode and a calomel electrode as the reference electrode. Changes in hydrogen ion concentration caused by changes in the potential of the glass electrode, resulting in changes in the potential between it and the electrode of mercuric acid, should be consistent with the formula (2-6)
