Electromotive force apparatus

Cathodic protection apparatuses are well proven, widely used devices and are not to be confused with magnetic devices gadgets ) or other similar but generally less than satisfactory items of capital equipment. Cathodic protection devices reverse the tendency of a metal to go into solution at the anode (corrosion) by the application of a counter-potential. This counter-potential or electromotive force (EMF) is provided either from a permanent external source such as a battery or rectifier or from the installation of a sacrificial anode. 

Figure 5. The apparatus for the electromotive force(EMF) measurements(An S02 gas concentration cell method).

Mercury is the only metal which is liquid at room temperature (cesium melts at 28.5" C, and gallium at 29.8°). It is iinreacrive, being below hydrogen in the electromotive-force series. Because of its unreactivity, fluidity, high density, and high electrical conductivity it finds extensive use in thermometers, barometers, and many special kinds of scientific Apparatus. 

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