For my past sins, Leslie Ettre has given me the privilege of writing a few words to preface his excellent little book. It gives me great pleasure to do so, because of the many years of fruitful collabo­ ration we have had at Perkin-Elmer, because it is refreshing to see a treatise in gas chromatography in which the theoretical treatment has been bared to its essentials, without a mushrooming of formulae which, by means of an ever increasing number of parameters, account for more and more, and explain less and less, and because the author has recognized that the gas chromatographic column is a nearly passive element in its own right which deserves to have a treatise written nearly exclusively about it, just as electrical circuit theory can be discussed without elaborate references to vacuum tubes and meters. I wish this conscientiously written volume the success it deserves. M. J. E. GOLAY VII Preface Gas chromatography is a separation technique used primarily in analytical chemistry. Therefore, it is evident that special emphasis should be placed on that particular part of the apparatus in which the separation takes place. This part is the column, the heart of the gas chromatograph. The goal of researchers in the field of gas chromatography has been-from the beginning-to understand the separation process so that they might design columns with the best possible performance. Such investigation led M. J. E.