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edition. I t is intended as a textbook for students and as n reference work for persons in the industry. I t is a unit in itself and could be used independent of Volume I. -1s a matter of fact, in Chapters 11 (“Review of theoretical electrochemistry”) and SIT- (“Electroanalysis”) there is coiisitierablc overlapping with the material in I-olume I . The book is well organized and contains much information of value to those for whom i t is written. I t gives a concise and well-illustrated description of the many applications of electrochemistry, without entering into tlic theoretical fundamentals. However, adequate references to journals and books enable the reader t o find sources of discussion of the basic principles. T h e two volumes together adequately cover the field,--”Principles and Applications of Electrochemistry . ’ ’
I. 11. KOLTHOFF.
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:lIagnetocheniistry. By P. R.SELWOOD. is 287 p p . ; SO fig. Sen- Torl;: interscience Publishing Company, 215 Fourth Avenue, 1913. Price: $5.00. This book is what i t purports to be: namely, a book on magnetoche~nistr,~anti not a book on magnetism in general. The author defines magnetochemistry as the ”application of magnetic susceptibilities and closely related quantities to the solution of chemical problems.” He explains that he adopts this soniexhat restricted definition in order to keep the volume within “reasonable bounds”, and adds that in consequence ‘ . S o more than mention will be found of several branches of magnetism, particularly of magneto-optical phenomena, of the gyroniagnetic effect, and of adiabatic demagnetization. . , . The field of atoniic inagnetisni has been slighted so far as the theoretical side is concerned“. On the other hand, the author says he has tried to omit no major branch of iiiagnetochemistr?-. as defined, and he has certainly kept his word. I t is most illuminating to peruse the book and so realize how tremendously this subject has developed in the last decade. In the preface Professor Selwood notes that from 1931 t o the end of 1912 over one thousand papers on magnetochemistry have appeared. These various articles are documented in the nunierous footnotes. T o workers in the field, the volume, quite apart from its other interests, would be worth while just as a bibliography. I t is a truism t h a t writing a volume of this character must have represented a n enormously more difficult task than simply collecting one’s own investigations in a book, as so many writers do. With such a complete bibliography, i t is but natural t h a t there be an occasional liiisclassification or error. For instance, Jordahl’s work on copper is listed among the rare earths. Also, the reference on the measurements of Krishnan and collaborators on the anisotropy of gadolinium salts does not include the revisions they gave in a subsequent paper Tvhich reduce the anisotropy by a factor of the order 10 to a magnitude comparable with the theoretical value calculated by W , D. Lewis (cf. Phys. Rev. 67, 1088 (1910); 69, 770 (1941)). The first chapter of the book is devoted to the measurement of magnetic susceptibility. Besides the standard classical methods, a discussion is included of determinations of magnetic moment by means of the catalysis of the ortho-para reaction of hydrogen. Chapters I1 and 111treat atomic and molecular diamagnetism, with, naturally, emphasis on the behavior of complicated aromatic compounds. Chapters I V and V follow on atomic and molecular paramagnetism. .1very complete discussion is included of paraniagnetisiii as an indicator of free radicals. This is, of course, a field in which magnetic studies have been particularly instructive on moot chemical questions, and is perhaps the particular application which one thinks of first of all when the term “magnetochemistry” is nientioned. Chapter VI is devoted t o complex compounds. The discussion is almost entirely on the basis of the Pauling electron pair. I t would have been illuminating if more could have been said concerning n h a t this model really means in terms of average electronic charge distribution-possibly with some correlation with molecular orbitals. F o r instance, Fe(CS)8+- certainly cannot have as polar a structure as Fe- - - -(CX-:~F,,which is what would seem to be indicated by the Pauling model if taken too literally. Also: the author might properly have included some discussion of how the difference in behavior of cobalt and nickel compounds, or of six- and four-eobrdinatetl cobalt complexes, can be cxplained
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in terms oi i i i v ~ ~ ~ s iofo nthe crystalline Stark pattern. C'hapter YII treats nietnllic diaand para-iiingiieti,~iii.n-hile chapter 1-111is concerned xvith ferromagiietisiii. S a t u r a l l y in a chapter of twentl- pages 110 attenipt is niade to cover tlie entire subject of ferroniagnetisin, and inste:itl. e:iiphasis is properly Inid on the relation of Eerron~agnetisnxto alloy structure, etc. Chapter I S . rrii applied inagnetometric analysis, is perhaps the iiiost interesting and unusual of tlie \\-hole book. It is impressive to see how magnetism can be applied to the analysis of rare earths. metallurgical and mineralogical control, phase ratios and stoicliiometry, and especially how i t can even be used t o provide infor~nationo n the structure of catnlytically ncti7-e surfaces. The viewpoint of the book inclines to the empirical rather than theoretical, the chemical rather thnn the physical, aiid the encyclopedic rather than the critical. T h e physicist will be rather t e r r i f i d a t the enuiiieration of chemical compounds, for instance, on page 7 0 , and uill probably not be interested in the niagnetic properties of pentaerythritol tetraphenylether. as he will probably feel that the modus operandi of magnetism \vi11 be more lucid froin t h e study of some less forinidable compound. Also, the person interested in "why is ferromagnetism" will find only a sentence stating t h a t the essential condition for it is that the wave functions of electrons in neighboring atonis should only slightly overlap each other near the nuclei. However, this emphasis in viewpoint is proper in view of the avowed purpose of the book. I t is perhaps well t o caution t h a t theory hasnot explained completely the magnetic behavior of even such a simple solid as CeF3,so that the perfectionist \vi11 not get the same comfort from magnetochemistry as he does from spectroscopy. Severtheless. i t is perfectly possible for magnetism t o furnish crude b u t illuminating information 011 n coinplicated reaction, even though the details are incomplete. Professor Selwood is t o be congratulated on writing a book which fulfills a distinct need not covered by other volumes! and which is devoted t o a n interesting and growing field, for magnetochemistry has earned i t s right to stand beside the study of dielectric constant, spectra, and diffraction as a powerful tool for the chemist.
J. H. TAXVLECK.
