JOURNAL OF CHEMICAL EDUCATION
180 on the second law. Gas compressors, vapor-recompression evaporators and refrigeration (hut not the more general idea of the heat pump) are also discussed here. In the chapter on thermodynamics of solutions, the oompressihility of gaseous mixtures is f i s t discussed, followed by their critical phenomena. Liquid solutions are discussed briefly. The thermodynamic functions chemical: potential, fugacity, and activity are defined m d their application to nonideal systems is illustrated. The chapter on physical equilibrium deals largely with vaporliquid equilibrium, hoth at normal and high pressure, and solubility. Chemical equilibrium illustrates the application of thermodynamic dsta to the calcul;ltions of equilibrium oompositions for a given reaction. The newer methods of presenting the fundamental data are discussed. Equilibria in liquid solutions are considered briefly. The final chapter on thermodynamic properties from molecular structure is a brief treatment of the use of empirical coorrelations and statistical methcds to obtain thermodynamic data. Although the empirical correlations may he useful if no data are available it is doubtful if a, graduate student or professional chemical engineer can use the statistical methods to find what he needs. However, it may stimulate the graduate student to further study in this important field. For a text to be used at the senior level, the reviewer believes that the st.udent should he shown the classical (nonspectroscopic) experimental methods by which the values of thermodynzmnie functions have been determined and the agreement found among these methods. Then the tables of data. mean something in terms of what has been done to obtain them. Thus, the third law of thermodynamics is discussed in half a page and does not leave the student with the feeling that he knows how entropy could be determined. A t the senior level the instructor must use cam in selecting the material in each chapter that can he assimilated by his students in the time available. A repetition of d l the material at the firsbyear graduate level would fix many of the concepts which the student previously did not fully comprehend hoth as to their broad significance and their application. The chemical engineer and physical chemist in industrial work will weloome the practical viewpoint this hook has and the C. P. P. charts which will enahle him to calculate (or a t least approximate) the thermodynamic data he needs for his chemical or physical process. The reviewer will reiterate from his review of Part 111: "Every physical chemist should have the three parts of 'Chemical Process Principles' to learn whet the chemical engineer does with his physical chemistry." In this is implied that the chemical engineer already has the three parts and is using them.
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THE THEORY OF VALENCY AND THE STRUCTURE OF CHEMICAL COMPOUNDS
Pandit RGy, Professor and Head of the Department of Pure Chemistry, University College of Science, Calcutta, India. Published by the Indian Association for the Cultivation of Science, 81 pp. 22 figs. 98 refs., no index. 17 Calcutta, 1946. i v X 24.5 cm., paper bound.
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THESE CHAPTERS (Coach-Behar Professorship Leotures) about hoe and q h y atoms combine, "pass in 8. brief review the various stages of the theory of valency from t,he days of classical mechanics to the present time, with special reference to its later developments!' The first three chapters explain the historical origin and meaning of the term valenoy, snd elaborate on Werner's ooordination tbeory. The subsequent quantum mechanical concepts are given with a minimum of mathematics, with same helpful wave pattern illustrations, and with mind-opening vigor. Complex (coordination) compounds predominate among the types of structures discussed in this hook, since Professor RBy himself made numerous original mntributions in this field (in 1928) he challenged the simplicity of the Bose-Wela-Baudisch E. A. N. rule). The bond type transition hetween double salts and "stable" complexes is well emphasized, hut the preferred new nomenclature for these compounds is not mentioned. Molecular orbital theory is exphined and compared with spin theory and looalised atomic orbital theory. RBy mentions how it alone succeeds in correlating isosteres (molecules with similar physical propertie~,spectra, and electron configurations), such as Na with CO and HCN; or 0 2 with HaCO, C2H4,and B1H6; or F2 with C2Ha,etc. While magnetic properties of coordination complexes can he explained by the molecular orbitals as well as by Pauling's localized honds, RBy prefers the latter because of other evidences such as tracer chemistry-an excellent tool for this field-and for the direction-indicating value of localized honds in general. Multiple and metallic and ionic-crystal bonds are hriefly reviewed, as are resonance (benzene, etc.) and color. Certain other equally intriguing vdency problems could not be covered in this short survey, such as classifying "isoteric groups" of molecules like Periodic Groups of atoms. No mention is made of a recent preference for the old double hond structures instead of coordinate links in the familiar ooy-acids (Annual Reports, 1945, p. 66); nor of the relations between hond length, charge, and refractivity; nor of the electron "sextet" as the fundamental ohar~rscteristicin aromatic structures (Remick, 1943, pp. 154160). Nevertheless this little hook should serve well ss the author intended, "to stimulate the interest of advanced students and teachers of chemistry in the subject." WILLIAM WISWESSER WILLSONPRODOCTB, INC. Rsaonro, PENNSTLTANIA
