Electrodes for pH/Redox

The pH value indicates the acid or alkali content of a solution and normally ranges from pH 0 to pH 14.

Pure water has a pH value of 7 and is defined as being neutral. The pH value of a solution can be
increased by adding alkali and reduced by adding acid. Two electrodes are always needed in order to measure the pH value: a measuring electrode and a reference electrode. An electrical potential proportional to the pH value is generated when these two electrodes are immersed in a solution and can then be measured with the aid of appropriate amplifiers. If both electrodes are accommodated
in a single shaft, this is known as a combined electrode. They are now used almost exclusively today, since combined electrodes are very much easier to handle than separate electrodes. In such combined electrodes, the glass electrode is centrally immersed in the reference electrolyte.