The widespread use of the copper sulfate half cell as a reference electrode in corrosion measurements has resulted largely from the publication of a paper by Ewing1 in 1939 in which he recorded observations on its temperature coefficient, polarization and resistance characteristics. He proposed this electrode as the most practical of several considered and pointed out that significant errors could be encountered under some conditions of use.
Pope2 presented a paper at the 1955 NACE conference in Chicago showing the variations in the potential between two lead chloride half cells in contact with the earth. He showed that the potential differences varied with position, with time, and with whether the earth was moistened with tap water or a saline solution. It was found that the range of variation in these cells was approximately 35 millivolts.
In connection with previous work of a Task Group of NACE Technical Unit...
