Electromotive Series of the Elements

Standard [reduction] potentials for hundreds of electrodes have been determined (mostly in the period 1925-45, during which time they were referred to as oxidation potentials ) and are usually tabulated in order of increasing tendency to accept electrons. This ordering is also known as the electromotive series of the elements. As can be seen in the abbreviated version in Table 1, sodium is the most active of the metallic elements in the sense that its oxidation product Na+ shows the smallest tendency (as indicated by the highly negative voltage) to undergo reduction. 

The first step in this new stain protocol employs copper acetate, a metal salt that is both a good fixative ( ) and a silver stain enhancer. The mechanism of copper s stain enhancement, in this and other silver stains, may be similar to its action in the biuret reaction (15.), in which a characteristic color shift, from violet to pink, is achieved by titrating peptides in the presence of copper ions. Copper complexes formed with the N-peptide atoms of the peptide bonds are primarily responsible for this reaction. There are also some number of secondary sites which may interact with copper. Any elemental copper formed may displace positive silver ions from solution as copper has a greater tendency to donate electrons than silver, indicated by its position in the electromotive series of the elements. Following the treatment with copper acetate, the membrane is sequentially soaked in a solution containing chloride and citrate ions and then in a solution containing silver nitrate. The membrane is then irradiated with light while it is in the silver nitrate... 

According to the electromotive series of the elements there are innumerable pairs which will yield electrochemical energy accumulators. For instance, take a metal and a metallic oxide and immerse them in a liquid electrolyte. These are the main parts of a cell as Figure 15.1 demonstrates. 

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