646 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS principles of gradient elution, stressing that there is no very fundamental distinction from conventional stepwise variation of cluehr. The main practical advantages are elimination of uncertainty in determining when (stepwise) changes ideally should be made and the avoidance of spurious peaklets where this point has been misjudged. He then reviews the considerable literature regarding the choice of apparatus and techniques and concludes a lengthy account with general advice for selecting an optimum compromise among elution conditions. A glossary of preferred symbols and an extensive bibliography are appended. J. P. Adloff, a French radiochemist, discusses successively radiochromatographic applications of gas phase (previously reviewed by him in Volume 4), paper partition, electrophoretic, adsorption and ion exchange separations, for the study of a very comprehensive series of products of the Szilard-Chambers effect, i.e. the chemical or kinetic resultants of nuclear recoil reactions. The first volume included a review of chromatographic separation of chloroplast pigments published prior to 1959 Z. Sestak of the Czech Academy of Science brings up to date p.p.c. methods for chlorophyll and carotenoids. He refers to other reviews and relevant portions of handbooks, to suitable types and treatment of paper, to the manner of application of solutions, to the development of apparatus and new devices, to a variety of solvent systems, to factors influencing separation and to interesting applications. However, the main bulk of the article comprises a remarkably detailed tabulation of published adsorption, reverse phase and more specialized methods for separating chloroplast pigments. It remains to be seen whether the paper techniques reviewed therein are going to be superseded by t.l.c. procedures. The introduction (1955) of two-dimensional p.p.c. constituted a great step forward for plant biochemistry V. H. Booth (Cambridge) describes the contribution this technique has made in his and other hands to the separation and simultaneous display of a wide variety of known and unidentified fat soluble plant products. With obvious enthusiasm and a chatty style, the author summarizes the discoveries- and some of the pitfalls- in the elucidation of lipid structures. He admits that some of his conclusions are speculative and draws attention to gaps in our knowledge of lipid distribution and function. Curiously he does not seem to consider t.l.c. when indicating future development. V. Betina (Bratislava University) presents an extremely comprehensive review of the great contribution that p.p.c. has made to the elucidation of antibiotics, particularly the means to characterize many new ones and to demonstrate identity of some that have been independently isolated. Antibiotics belong to many diverse groups of organic structures, having little in common save their biopotency - which, however, does permit the development of bioautographic detection procedures. General aspects are considered first and then the results with better known anti- biotics a great variety of chromatographic methods of classification are tabulated followed by an indication of aids in the search for new metabolites. There are tables of numerous solvent systems, many diagrams illustrating, for instance, the variation of Rf with pH and altogether 578 references are cited. The close association and low concentration of steroids render efficient separation essential t.l.c. is now one of the most important analytical procedures. E. Heftmann (U.S. Dept. of Agriculture) assesses the relative advantages of t.l.c. and other separa- tion methods thus g.l.c. may generally be more accurate and convenient for quantita- tive analysis but non-specific detectors require preliminary t.l.c. or liquid column

BOOK REVIEWS 647 separation. I-Ie discusses the choice of supports, solvents and detection techniques. Examples are given of the separation of the individual steroIs, sapogenins, alkaloids, bufotoxins, bile components, cortical hormones, androgens and estrogens. Republication of lectures this year has been avoided all six articles have been written specially for this number- several of them by earlier contributors. Despite an overall 10 •o reduction in the number of pages compared with previous volumes in this series, the average length of individual reviews has increased slightly. Judged as a critical survey of progress and diversification of chromatography in specific fields over the past several years, the high standard set by preceding reviews has been skilfully maintained. G.F. PHILLIPS.