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Powder Photographs. The chapters under “Structure Determination” are :VI. Determination of Unit Cell Dimensions; VII. Determination of the Positions of the Atoms in the Unit Cell by the Methods of Trial and Error; VIII. Evidence on Crystal Structure from Physical Properties; IX. Some Examples of Crystal Structure Determination by Trial; X. Electron Density Maps and Vector Maps; and XI. Broadened X-ray Reflections and their Interpretation. The reviewer feels that the chapters on crystal shape, crystal structure determination by t,rial and error methods, and electron density maps and vector maps will, because of their lucidity, prove particularly valuable to beginners and possibly t o other workers in the field. The book seems to be remarkably free from errors. The use, on page 185, of the term “molecular weight” as synonymous with the absolute weight of a single molecule is confusing and unnecessary. Some minor errors are as follows: I n Fig. 129, page 214, the lower curve, labeled 200, should be labeled 002; line 7, page 232, should read ‘L bc diagonal”; Table V, line 7, page 240, should read “hkl when 1 odd”; and line 4, page 353, s h o u d read “Fig. 218 (right).” Theprinting and binding have been well done. Thus, from all angles, the book is one which the reviewer can heartily recommend. HAROLDP. KLUG.
Advances in Colloid Science. 1‘01. I I . Scientific Progress i n the Field of Rubber and Synthetic Elastomers. By H. MARKA N D G. S. WHITBY(Editors). 453 pp. New York: Interscience Publishers, Inc., 1946. Price : $7.00. This book is a collection of review articles by different authors on scientific progress in the field of rubber and synthetic elastomers. Following the introduction by G. S. Whitby, there are chapters on “Second Order Transition Effects in High Polymers” by R. F. Boyer and R. S. Spencer; “Crystallization Phenomena” by L. A. Wood; “The Study of Rubberlike Substances by X-ray Diffraction Methods” by C. W. Bunn; “The Thermodynamic Study of Rubber Solutions and Gels” by G. Gee; “Significance of Viscosity Measurements” by R. H. Ewart; “Kinetic Theory of Rubber Elasticity” by E . Guth, H. M. James, and H. Mark; “Vulcanization” by H. Farmer; “Rubber Photogels and Photovulcanizates” by H. P. Stevens; and “Reinforcing and Other Properties of Compounding Ingredients” by D . Parkinson. The wide range of subjects covered makes i t certain that this volume will contain sornething of interest and importance to everyone working in the field of high polymers. Two chapters especially, that of Gee on thermodynamic properties and that of Ewart on the significance of viscosity measurements, serve as excellent critical r6sum6s of fields in which much work has been done and still remains to be done. The chapter by Farmer is a very good summary and evaluation of what is known from the chemical point of view about the process of vulcanization. I n short, the articles in the book are uniformly excellent. Each is accompanied by a quite complete bibliography. The book can be recommended unreservedly to all those interested in the field of high polymers. E . J. MEEHAN. Physical Conslants of Hydrocarbons. Vol. I I I . Mononuclear Aromatic Hydrocarbons. By GUSTAVEGLOFF. A.C.S. Monograph No. 78. xiv 661 pp. K’ew York: Reinhold Publishing Corporation, 1916. Price : $15.00. This volume extends to the mononuclear aromatics the very useful collection of data on physical properties already published by Dr. Egloff and his coworkers for simpler hydrocarbons. The physical properties included are melting point, boiling point, density, refractive index, and, where available, values for the critical constants, optical rotation, sublimation temperatures, and temperature and pressure coefficients for the appropriate constants. There is little for us to do in reviewing this book other than to point out the obvious facts that the hydrocarbons covered here are extremely important ones and that the book will
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prove a correspondingly useful reference work. As an interesting commentary on the importance attached to these data, we note that over 400 papers are cited regarding the physical constants of the parent aromatic, benzene. We cannot suppress a note of regret for the high price of this volume. BRYCEL. CRAWFORD, JR.
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Physical Chemistry f o r Premedical Students. By JOHNPAGE AMSDEN. x 298 pp.; 54 fig. New York: McGraw-Hill Book Company, Inc., 1946. Price: $3.50. This slim volume is designed by its author to treat those portions of physical chemistry which are of value to the premedical student; i t includes, after the more or less usual chapters on dimensions and units, gases, and liquids, chapters on solutions, properties of solutions, both non-electrolytic and electrolytic, chemical equilibrium, hydronium ion (including a very elementary treatment of galvanic cells), oxidation and reduction, reaction rates, and eo oids, including some membrane phenomena. We believe that Prof. Amsden’s selection of topics to include in his text is quite good, wisely omitting all material with which the medical student will not come into contact. The various formulas which are developed are well illustrated by numerical examples, rather clearly worked out; each chapter has a t its conclusion a number of problems on which the student can exercise his understanding. We should not favor quite as much strictly physiological material as Prof. Amsden has included in, for example, the last few pages having t o do with osmotic pressure, or in the last page or two of the chapter on colloids; but this is a matter of taste, and is certainly not too serious. We feel we must vigorously criticize the oversimplified derivations given for many of the important relationships in this text. We agree thoroughly with the position Prof. Amsden takes in his preface, that “for the student to appreciate fully the possibilities and limitations of the equations of physical chemistry i t is essential that he be familiar with their derivations.” We also agree with Prof. Amsden that simplified derivations may be best for premedical students, whose mathematical background is never too sure; but we fear that Prof. Amsden’s derivations are simplified to the point of inaccuracy in many cases, and in some cases to the point where they smack of an intellectual swindle. Thus the derivation given for the osmotic-pressure relationship on pages 91-93 would lead the student to believe that the equation arrived a t (No. 37) is exact for the approximations of a perfect gas for the vapor and of a perfect solution; as a matter of fact, the equation is not exact under these circumstances, and we believe that the premedical student can profit from a knowledge of the more exact osmotic-pressure relationship. Again, the derivation of the Nernst equation given on pages 186-189 caused us definitely to squirm. Another criticism we must make, again arising from our dissatisfaction with Prof. Amsden’s simplifications, is of the section on oxidation and reduction energy changes, given on page 226 and following. The brief discussion of calorimetric and potentiometric energy determinations is most likely to lead the student to believe that the heat of a reaction and its free energy are equivalent (though of course this statement is not made in just these terms). We do not believe i t wise to leave such a misconception in a student’s mind. Perhaps this is a difference in pedagogical viewpoint; Prof. Amsden may feel that it is better to give his students a simple half-truth which they can understand, than to risk confusing their minds with a distinction that they will, probably, never encounter in medical work. We do not; we would prefer that students get a misty glimpse of a difficult truth rather than a clear understanding of a simple falsehood. To teachers who feel that our viewpoint is too meticulous, and who agree with Prof. Amsden that oversimplification is justified in persuading premedical students that they know something of physical chemistry, his book should be worthy of consideration. BRYCEL. CRAWFORD, JR.
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