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.