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Partial Differential; (5) Infinite Series; (6) Partial Differential Equations; (7) Numerical Analysis; (8) Graphical Treatment of Chemical Engineering Processes; (9) Theory of Errors and Precision of Measurements. C. C. FURNAS.
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Ferrorcagnetismus. By R. BECKERA N D W. DORING. 25 x 17 cm.; viii 440 pp. Berlin: J. Springer, 1939. Price: unbound, 39 RM.; bound, 42.60 RM. In the investigation of ferromagnetism there are two groups of questions to be considered: the first is concerned, broadly speaking, with the occurrence of intrinsic spontaneous magnetization, and its magnitude and temperature variation, and the second with the details of the variation with field of the bulk magnetization and with various secondary effects. This book deals mainly with the second group. There are six sections. The first two deal briefly but illuminatingly with fundamental principles and with the general theory of ferromagnetism. The third section, more than a third of the whole book, deals with magnetization processes in ferromagnetics and the factors controlling them. An excellent opening chapter introduces questions connected with crystal, strain, and field energy, describes boundary movement and gradual change of direction of magnetization in spontaneously magnetized regions, and indicates the part they play in the course of magnetization. These topics are discussed in detail in subsequent chapters with reference to initial permeability, coercivity, high frequency permeability, and magnetic after effects. The thermal, electrical, and strain effects accompanying magnetization are then considered, and also the peculiar effects of a magnetic field on elastic properties and on the damping of mechanical oscillations. The final section, which deals with magnetic materials in relation to technological applications, opens with an account of precipitation processes in alloys and their effect on magnetic properties. Technological requirements for different purposes are clearly set forth, and the properties of a large number of both commercial and laboratory alloys are discussed in the light of the general theoretical outlook. From the point of view of a specialist the book is particularly useful for the remarkably comprehensive theoretical treatment, much of which is here published for the first time, of the interrelations between magnetization and strain, both applied and internal. The formal completeness in this one direction does, however, to some extent distort the impression given of ferromagnetism as a whole. None the less, the general parts of the book give good surveys of the present position, and show a wide appreciative knowledge of relevant work, though the selection of references to the literature sometimes seems rather arbitrary. The three hundred and nineteen diagrams, with explanatory captions, are an admirable feature. The table of contents makes the general plan clear, but the index is very inadequate. The book a t once takes its place as a valuable contribution to the literature of magnetism. It will be of great interest, however, not only to magneticians, but also to all those concerned with the properties of metals and alleys. EDMUND C. STONER.
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Reine Metalle. Edited by A. E. VAN ARKEL. 24 x 16 cm.; vii 574 pp. Berlin: Julius Springer, 1939. Price: unbound, 48 RM.; bound, 49.80 RM. The increased interest in the metallic state which has been so conspicuous in recent years has called for a more complete knowledge of the properties of pure metals. Absolute purity being unattainable, and the removal of traces of foreign elements from several of the metals being very difficult, it is important to know what degree of purification has been reached in esch instance, and how products of high
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quality may be obtained. The present monograph, in which twenty workers of several countries have collaborated, does more than this, as it includes under each metal a full account of such physical and mechanical properties as have been determined with sufficient accuracy, although not always on material of identical purity. This part of the work has been exceedingly well done, and will be found invaluable by metallurgists and by physicists who are working o p the properties of metals. The monograph is weaker on the chemical side. When a preparation is described by an author as, say, 99.97 per cent pure, the statement cannot be accepted without close examination. It is necessary to know the methods of analysis which were used, and the degree of care which was taken to ensure that no impurities were overlooked. With products of such a degree of purity, a direct analytical determination of the principal metal is of no value. It must always be estimated by difference, and any omission to determine an impurity which is actually present leads to a fictitiously high value for the purity. It is only rarely that a satisfactorily full analysis is made. The task has been greatly aided by the recent development of quantitative spectrographic analysis, but even this is limited by the difficulty of preparing standards containing known small quantities of impurities. Also, some of the non-metallic impurities are overlooked by this method, while hydrogen, nitrogen, and oxygen, which may profoundly influence the properties of a metal, are rarely looked for. The problem of “blanks” is the most important factor in such analyses. This side of the subject is rather scantily treated in the present work, in which the statements of authors as to the purity of their metals are accepted rather a t their face value, and the difficulties of analysis are not fully treated. A most interesting, and a t first sight surprising, fact is the very high degree of purity of certain metals now produced industrially. It would be quite impracticable to prepare aluminum in the laboratory of such high purity as the metal electrolytically refined by the A.F.C. process, described here by Gadeau, which contains less than 0.01 per cent of foreign elements. The cost of such a metal is not greatly above that of the commercial product, which has itself steadily risen in quality in recent years. Several other metals, including magnesium, zinc, and cadmium, have reached a similar stage in their industrial preparation. The situation is different in regard to metals of high melting point. No industrial variety of iron is pure enough for exact research, and tedious laboratory methods have t o be used for its purification. The editor of this book, who is now Professor a t Leyden, has been particularly associated with a method for the preparation of the more refractory metals, such as tungsten, thorium, and zirconium, by the thermal dissociation of their halogen compounds; this process has been found t o be widely applicable, and to lend itself well to the production of single crystals. The physical properties of tungsten, in spite of its refractory character, are better known than those of almost any other metal, its importance to the electric lamp industry, with its many well-equipped physical laboratories, being responsible for this. There are still some metals which are hardly obtainable in a satisfactory state for modern research, and in some instances, such as that of beryllium, minute traces of difficultyremovable impurities hamper the investigator. The accounts written and collected by Dr. van Arkel are of the highest value, and this well-printed volume should receive a cordial welcome. C. H. D ~ S C H . Principles of Mineral Dressing. By A. M. GAUDIN. First edition. 554 pp. New York: McGraw-Hill Book Company, Inc., 1939. Price: $5.00.
