me preface to this volume announces a departure from the standard editorial pattern set in earlier volumes. This has been effected in order to provide a greater concentration of editorial effort in the "major subfields of chromatography". The object of this change is to improve the technical content, but to retain the original aim of providing "stimulating, critical, readable and relevant reviews" of chromatography. This stated aim has been well met and this volume is certainly not lack&g in technial content. The topics covered range from the minority interest of supercritical fluid chromatography to the more generally practical qualitative gas chromatography. The first chapter, Practical aspects in supercritical fluid chromatography (37 pp.), by T. II. Gouw and R. E. Jentofi, is well structured and presents a complete review of the subject in a very readable form. However, the introduction describes the advantages of working in the supercritical phase as being the ability to chromatograph compounds of higher molecular weight than is possible with gas chromatography and suggests that, because of the enhanced solubility, higher separating speeds can be achieved than in liquid chromatography. Since the applications cited in most published work do not specifically illustrate these points, a more detailed discussion on the instrumental difticulties preventing these achievements would have been worthwhile. In section B of this chapter it is stated that the column sizes used are similar to those used in high-resolution liquid chromatography. As the column sizes given in most cited applications are measured in metres as opposed to the 10-20 cm of the present day liquid chromatographic columns, one must speculate whether the validity of the technique has been judged against liquid chromatography before the development of high-resolution columns with microparticulate packings. Despite these comments this chapter does present an interesting resume of an intriguing aspect of chromatography. Chapter 2, Gel permeation chromatography: A review of axial dispersion phenomena, their detection and correction (26 pp.), by N. Friis and A. Hamielee, presents the theoretical examination of the subject. This is well presented and gives a good description of the terms used. The treatise is entirely concerned with the gel permeation of polymers, which is of course the main province of gel permeation. It would have been interesting perhaps if application to the non-polymer use of gel permeation had also been considered, but this would not have been available from the literature and would then have gone beyond the scope~of this section. Chapter 3, Chromatography of heavy petroleum fractions (94 pp.), by K. N. Altgelt and T. R. Gouw, is by far the largest chapter in this volume. It makes the