ABSTRACT
The measurement of pH is arguably the most widely performed test in the chemical laboratory, reflecting importance of water as a ubiquitous solvent and reactant. In its most common interpretation, pH is used to specify the degree of acidity or basicity of an aqueous solution. Electrochemical measurement of pH utilizes devices that transduce the chemical activity of the hydrogen ion into an electronic signal, such as an electrical potential difference or a change in electrical conductance. The most widely used method for measuring pH is the glass membrane electrode. The hydrogen-ion-selective glasses used to construct pH indicator electrodes are formed by fusing silica, alkali metal oxides, and alkali earth oxides. The most widely used reference electrode for pH measurement is the silver/silver chloride electrode. The necessary contact between the filling electrolyte of the reference electrode and the sample forms a liquid junction and results in the development of a junction potential that depends on the compositions of the two electrolytes.
