7 The Electrified Interface.- 7.1 Electrification of an Interface.- 7.1.1 The Electrode-Electrolyte Interface: The Basis of Electrodics.- 7.1.2 New Forces at the Boundary of an Electrolyte.- 7.1.3 The Interphase Region Has New Properties and New Structures.- 7.1.4 An Electrode Is Like a Giant Central Ion.- 7.1.5 The Consequences of Compromise Arrangements: The Electrolyte Side of the Boundary Acquires a Charge.- 7.1.6 Both Sides of the Interface Become Electrified: The So-Called "Electrical Double Layer"--7.1.7 Double Layers Are Characteristic of All Phase Boundaries.- 7.1.8 A Look into an El.

Progress in Reaction Kinetics, Volume 4 is a 10-chapter text that focuses on the reactions of nitrogen atoms in the gas phase and some chemical factors in the kinetics of processes at electrodes. This volume describes first the free radical reactions dealing with halogenomethyl and alkoxyl radicals. The next chapters deal with electronically excited states, proton transfer, and kinetics of electrode processes. These topics are followed by discussions on the primary processes in the gas phase photochemistry of carbonyl compounds, as well as the mechanisms and rates of radiationless energy transfer. This book also looks into the methods used for the measurement of fluorescence lifetimes of aromatic compounds. A chapter examines the chemiluminescence in the oxidation of organic compounds and for other liquid-phase reactions. The last chapters discuss the role of the solvent in proton transfer reactions and some aspects of developments in the field of electrode processes. This book is of great value to reaction kinetics scientists and researchers.

The gradual emergence during the last decade of the study of the mechanism of electrode reactions from the dark ages has given stimulus to a consideration of the double layer at metal-solution interfaces, which extends far outside the classical experimental studies of the capacitance of the mercury solution interface made during the 1950's by D. C. Grahame at Amherst College, Massachusetts. The central aspect of the study of an electrode reaction is the elucidation of its path and rate-determining step. Two fields are, however, prerequisites for such studies. First, it must be known what species are in the bulk of the solution, for these will seldom be simple ones such as H30~ and this study ("complex ions") has been made with both extent and depth. Second, the occupancy of the surface of the electrocatalyst and the associated field gradients must be known as a function of position in the double layer. Such "maps of the double layer" can be given with reasonable certainty up to concentrations of about 1 N for mercury in contact with solutions of inorganic ions. However, this is-or was until very recently-the extent of the know ledge. The problems confronting a fundamental approach to the rational development of, e.g., fuel cell catalysis were therefore considerable.

As our knowledge of the mechanism of electrode processes increases, it becomes more and more apparent that the kinetic currents first observed by R. Brdicka and by K. Wiesner in the 1940's are very widely encountered. Very many electrode pro cesses contain a chemical stage. * This is true primarily of elec trode processes that involve organic compounds. Therefore, to understand the mechanism of electrode processes and, particular ly, to correctly interpret the results of polarographic investiga tions, it is important to know the characteristics and relationships controlling the chemical reactions taking place at the electrode surface. Generally, these reactions are substantially different from ordinary chemical reactions taking place in the bulk of the solution, since the reactions at the electrodes are often affected by the electric field of the electrode and the adsorption of the par ticipating compounds . The fact that hydrogen ions usuallY take part in the electro chemical reduction of organic compounds makes possible the use of electrochemical methods, particularly polarography, for the study of protolytic reactions. These reactions play an important role in organic chemistry: the majority of reactions of organic compounds in solutions go through a stage in which a hydrogen ion is removed or added (see, for example, [1, 2]). Therefore, the polarographic study of protolytic reactions can supply much important information to theoretical organic chemistry.

Despite reductions in the level of research activity in most fields which, for reasons of economic decline, have taken place in the U.S. during the last year or two, world progress in the fundamental aspects has continued actively. An important aspect of such recent work has been the use of nonaqueous solvents in studies on the constitution of the double-layer and electrochemical reactions. Interpretation of the behavior of electrode interfaces in such solvents demands more knowledge of the solvation properties of ions in nonaqueous media. Chapter 1 by Pad ova on "Ionic Solvation in Nonaqueous and Mixed Solvents" gives an up to date review of the present state of knowledge in this field, together with tabulations of data that are likely to be of quantitative value in further investigations of both homogeneous and heterogeneous electrochemistry in such media. Electrochemical studies of cathodic processes in nonaqueous solvents have, in recent years, revealed the role of solvated electrons. These are of interest in new approaches to reductive electro-organic synthesis. Similarly, the generation of hydrated electrons in photo cathodic processes is of great interest. In Chapter 2, by Conway, the conditions under which solvated electrons can arise in electrode processes are critically examined and the electro-organic reactions that hwe been investigated are reviewed. The supposed electro generation of hydrated electrons in the water solvent and as inter mediates in cathodic hydrogen evolution is shown to be unlikely.

The fourth volume of Modern Aspects of Electrochemistry is being prepared at a time of great growth of interest in electro chemistry. The situation can be summarized by saying that the realization is spreading among scientists that electrochemistry represents a broad interdisciplinary field, which has applications to many areas in physics, chemistry, metallurgy, and biology. Among the reasons for this awakening is the reorientation of what is understood under electrochemistry toward electrodics "the study of charged interfaces"-with the ionic-solution aspects of electrochemistry being regarded increasingly as aspects of physical chemistry which are helpful auxiliaries to the broad subject of charged interfaces. The pervasiveness of electrochemistry be comes clearer when one recalls that most interfaces carry a charge, or undergo local charge transfers, even though they are not con nected with a source of power. A further reason for the rapid increase in electrochemical studies arises from the technological aspects, in particular in energy conversion and storage, syntheses, extractions, devices, the stability and finishing of surfaces, the treatment of water, etc. The fact that electrodics allows the conversion of chemical to electric energy and the storage of the latter, at the same time producing fresh water as a by-product, presents an aspect of the subject which appears to have far-reaching significance.

The present volume contains five chapters covering areas of contemporary interest in the fields of electrolyte solutions, the state of solvent molecules at electrode surfaces, charged colloid interfaces, surface chemistry of oxide electrodes and electro chemistry, and bioelectrochemistry of charge transfer complexes. The first chapter, by Barthel, Wachter, and Gores, covers the topic of conductance of nonaqueous pro tic and aprotic electro lyte solutions. This field is not only of intrinsic interest in itself, illustrating the important departures of ion-transport behavior in organic solvents from that, more well known, in water, but the information and extensive new data presented in this chapter will be of interest to those working with nonaqueous alkali-metal batteries where the conductivity and ion-association behavior of electrolytes in various solvents other than water is of great importance. The second chapter is devoted to a very fundamental and ubiquitous aspect of electrochemistry of electrodes: the state of solvent molecules, adsorbed and oriented, at their surfaces. The role of solvent adsorption and orientation in double-layer proper ties, it will be recalled, remained poorly understood until the early 1960s. This chapter, by Trasatti, gives a thorough account of the present state of knowledge of solvent orientation at electrode interfaces and of the unsuspected (until recent years) role it plays in properties of the double layer and in determining the potential profile at charged metal surfaces in solution.

Corrosion, Volume 1: Metal/Environment Reactions is concerned with the subject of corrosion, with emphasis on the control of the environmental interactions of metals and alloys used as materials of construction. Corrosion is treated as a synthesis of corrosion science and corrosion engineering. This volume is comprised of nine chapters; the first of which provides an overview of the principles of corrosion and oxidation, with emphasis on the electrochemical mechanism of corrosion and how the kinetics of cathodic and anodic partial reactions control the rate of overall corrosion reaction. Attention then turns to the effects of environmental factors such as concentration, velocity, and temperature based on the assumption that either the anodic or cathodic reaction, but not both, is rate-controlling. The corrosion of ferrous and non-ferrous metals and alloys, as well as rarer and noble metals, is considered. The reader is also introduced to high-temperature corrosion and mechanical factors that affect corrosion. This book concludes with topics of electrochemistry and metallurgy relevant to corrosion, including the nature of the electrified interface between the metal and the solution; charge transfer across the interface under equilibrium and non-equilibrium conditions; overpotential and the rate of an electrode reaction; and the hydrogen evolution reaction and hydrogen absorption by ferrous alloys. This book will be of value to students as well as workers and engineers in the field of corrosion.