The objective of this second edition remains the discussion of the many diverse roles of electrochemical technology in industry. Throughout the book, the intention is to emphasize that the applications, though extremely diverse, all are on the same principles of electrochemistry and electrochemical engineer­ based ing. Those familiar with the first edition will note a significant increase in the number of pages. The most obvious addition is the separate chapter on electrochemical sensors but, in fact, all chapters have been reviewed thoroughly and many have been altered substantially. These changes to the book partly reflect the different view of a second author as well as comments from students and friends. Also, they arise inevitably from the vitality and strength of electrochemical technology; in addition to important improvements in tech­ nology, new electrolytic processes and electrochemical devices continue to be reported. In the preface to the first edition it was stated: . . . the future for electrochemical technology is bright and there is a general expectation that new applications of electrochemistry will become economic as the world responds to the challenge of more expensive energy, of the need to develop new materials and to exploit different chemical feedstocks and of the necessity to protect the environment. The preparation of this second edition, seven years after these words were written, provided an occasion to review the progress of industrial electro­ chemistry.