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NEW BOOKS
chemical properties of nitrogen (a very full account of the spectra being included), and with active nitrogen. The account of the technical production of nitrogen includes patent literature. There is a good discussion of the atomic weight of nitrogen in which analyses of a large number of researches are set out in a very clear and instructive form. This first section of the volumes on nitrogen is very complete and of high standard, and covers a very extensive field of literature. J. R. PARTINQTON.
Free Radicals. A general discussion held by the Faraday Society. 25 x 15.5 cm.; 2 248 pp. London: Gurney and Jackson, 1934. Price: bound, limp cloth, 12/6. Once more the Faraday Society has placed physical chemists under a debt of gratitude. The reports of the discussions which they organize a t frequent intervals are now well-known and highly appreciated, alike by those who are, and those who would be, up-to-date in their knowledge of the latest developments. By bringing together distinguished workers in a special field, hearing and answering questions, they not merely present the subject but present it alive. This volume is most timely and will be most welcome. It indicates how much preparatory work has already been achieved-work on the existence and preparation of free radicals-and these results are discussed by the men who have attained them. It also shows how the application of exact physiochemical methods to the available material may now be expected to lead to important conclusions. The first part (12 papers) deals with free radicals of relatively long life; the second with those of short life, and this is subdivided into chemical aspects (A) general and inorganic (5 papers), B, hydrocarbons (7 papers). The third part deals with the physical aspects of radicals of short life (5 papers). Part I opens with a n account of prevalent carbon radicals, followed by a short paper by Schonberg on a new class of radicals having a free sulfur bond. Sugden gives an account of magnetism in free radicals due to an odd number of electrons. Sulfur monoxide and oxygen are discussed; theoretical papers are contributed by Huckel, Lennard Jones, and Ingold; electronic levels are dealt with by Snow and Allsopp and the C=C double bond is specially considered, P a r t I1 opens with a n account by Norrish of the photochemical production of free radicals, followed by a theoretical paper by Franck and Rabinowitsch. Part I I B contains important contributions by Bone, Rice, Paneth, Hartel, Polanyi, and others. Part 111has a n introductory paper b y Mecke on free radicals and spectroscopy, and an account of the positive ray method of investigating the decomposition of hexane by Conrad (with some excellent photographs). There are papers by Harkins and by Willey on free radicals produced in the electric discharge, and one by Semenoff on the transference of energy in collisions. Taken together, the papers and discussions give a n admirable idea of the state of knowledge and opinion on a subject which has only recently begun t o attract much attention; they are very suggestive of developments in the near future. Much light is being thrown on the problems of molecular stability and molecular change. E. B. LUDLAM.
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Gasentladungstabellen. Tabellen, Formeln und Kurven zur Physik und Technik der Elektronen und Ionen. By M. KNOLL,F. OLLENDORFF, AND R. ROMPE (with the 171 pp. Berlin: Springer, collaboration of A. Roggendorf). 25 x 17 cm.; x 1935. Price: 29RM (in cloth). The authors have attempted to give in this volume, in a s convenient a form as possible, all the data likely to be required by workers with the discharge of ions and
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