Caesium preservation

The caesium assumption is popular with electrochemists and gives results comparable with the ferrocene-ferricinium assumption (ii) at least for solutions in water, formamide, methanol, and acetonitrile (Kolthoff, 1964 Strehlow, 1952 Koepp et al., 1960). However, we favour the tetraphenylarsonium-tetraphenylboride assumption of Grunwald et al. (1960) because it makes a more satisfactory allowance for size effects, such as making and breaking of solvent structure, while still preserving the attractive features, as to electrostatic solvation, possessed by the ferrocene-ferricinium couple and the caesium cation. 

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