Electrolytes Elementary Concepts

This book seeks essentially to provide a rigorous, yet lucid and comprehensible outline of the basic concepts (phenomena, processes, and laws) that form the subject matter of modem theoretical and applied electrochemistry. Particular attention is given to electrochemical problems of fundamental significance, yet those often treated in an obscure or even incorrect way in monographs and texts. Among these problems are some, that appear elementary at first glance, such as the mechanism of current flow in electrolyte solutions, the nature of electrode potentials, and the values of the transport numbers in diffusion layers. 

Much attention has been directed since olden times towards ion solvation, which is a key concept for understanding various chemical processes with electrolyte solutions. In 1920, a theoretical equation of ion solvation energy (AG ) was first proposed by Born [1], who considered the ion as a hard sphere of a given radius (r) immersed in a continuous medium of constant permittivity (e), and then defined AG as the electrostatic energy for charging the ion up to ze (z, the charge number of the ion e, the elementary charge) ... 

This chapter provides the groundwork of solution chemistry that is relevant to solvent extraction. Some of the concepts are rather elementary, but are necessary for the comprehension of the rather complicated relationships encountered when the solubilities of organic solutes or electrolytes in water or in nonaqueous solvents are considered. They are also relevant in the context of complex and adduct formation in aqueous solutions, dealt with in Chapter 3 and of the distribution of solutes of diverse kinds between aqueous and immiscible organic phases dealt with in Chapter 4. 

The concept of the electronic work function is very familiar to physicists and chemists and is discussed in elementary textbooks. A much less familiar concept is that one may measure experimentally the work required to remove an ion from an electrolyte solution. This is also discussed in this chapter but before doing so, the properties of liquids and solutions at gas interfaces are considered. 

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