During the forty years which have passed since Masuzo Shikata published his paper on the reduction of nitrobenzene at a dropping mercury electrode, the number of polarographic studies of organic compounds in the literature has risen to several thousands. The ever increasing amount of experimental data was in need of some unified method of classification which would yield unambiguous and possibly complete information on the polarographic behavior of organic substances. Dr. Zuman's book presents an original attempt to meet this need by providing a system based on correlations between the polaro graphic half-wave potentials of organic depolarizers and their Hammett constants. I consider this a very happy conception, for, more than any other book yet written, it brings polarography nearer to the organic chemist; and it will undoubtedly convince him that, in its application to his subject, the method is more than a mere analytical tool. The author hardly needs any introduction. During many years of research in the field of organic polarography, he has published numerous papers on a variety of problems; his latest interest is the application of the Hammett-Taft equation to polarographic measure ments, in which he has done pioneering work. It remains for me to hope that this book, which opens up new prospects for the fruitful application of polarography, may inspire vii viii Foreword some reader with useful ideas in his search for new paths in his research problems.

Even though the nwnber of requests for reprints and the number of quotations in the Science Citation Index has indicated an ever-increasing interest in topics of organic polarography, I have often felt that the reason that some work is less known may well be because the papers were published in less accessible journals. Therefore, I was pleased when I was asked to prepare a selection of my papers on organic polarography for reprinting. This collection of papers may indicate some of the possibilities offered by polarography in the study of properties of organic compounds. The fact that the papers are published in one volume, not only makes the information more easily accessible for the reader, but also enables a direct comparison of related topics. The mode of selection is discussed in the Introduction. The papers reprinted in this volume are mostly based on work carried out in the J. Heyrovsky Institute of Polarography of the Czechoslovak Academy of Sciences in Prague, in cooperation with my co-workers. I would like to take this opportunity of thanking all of them for the pleasure I got from this cooperation on the solution of varying problems of organic electrochemistry .