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project a success, and he merits the sincere thanks of all workers in the field of the chemical and physical sciences. The scope of the work as represented in the earlier publications is so well known to scientists that an extended review of the present volumes is unnecessary. I n these days when scientific data are scattered through a thousand “journals” it becomes imperative that someone undertake the task of collecting those data which appear t o possess more or less permanent value and making them available t o the researcher in some such form as those publications represent. It is a necessary consequence of this type of publication that volumes such as these should be rather expensive. However, their cost would represent an insignificant fraction of the cost of the time which the industrial or research worker without them would spend in searching the literature, so that the initial cost for their purchase will eventually be returned manyfold. It is an interesting commentary on human nature that the governing body of an organization will often quibble over a very moderate expenditure for books and a t the same time spend without a question thousands of dollars for machinery, equipment, or new personnel. The library is the heart of a university or of a research laboratory, and volumes such as these are a n invaluable adjunct to abstract journals. Special attention should be called t o the index volumes, the first being a collective index for Vols. I t o V. More than twenty thousand substances are classified here. It contains (1) an analytical index alphabetically arranged in four languages (in parallel columns), (2) an alphabetical index of all substances (animal, plant, mineral, technologic products, etc.) including many chemical “trade names” which the chemist does not always associate with the chemical formula, and (3) a formula index, (arranged according to empirical formulas) of all definite chemical compounds. These volumes, and those which preceded and those which will follow, should be on the shelves of every reference library and of the library of every research institution. Special prices may be secured by taking advantage of the subscription rates. Incidentally, i t may be noted that certain sections (note, e.g., section on spectroscopic data noted above) may be purchased separately if purchase of the entire volume is not desired. Ross AIKENGORTNER.
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Einjchrung i n die Elektronilc. By 0. KLEMPERER.25.5 X 17 cm.; xii 304 pp. Berlin: Springer, 1933. Price: unbound, 18.60 marks; bound, 19.80 marks. The sub-title is “The experimental physics of the free electron in the light of classical theory and of wave mechanics.” The experimental side of the subject is stressed throughout, the mathematical and theoretical sides being merely quoted in sufficient detail to give point to the story. Problems involving relatively abstruse sections of electron-gas kinetic theory are handled either very briefly, or not a t all; there is, for example, no mention of thermoelectricity. So far as concerns the mere experimental side of our acquaintance with the properties of the negative electron, the book may not inaptly be described as a small “Encyclopaedia Electronica.” It deals with a wide range of very diverse phenomena, here grouped for convenience-and of necessity somewhat arbitrarily-under three main headings: (1) the free electron; (2) electron emission; and (3) interaction between free electrons and atoms. The treatment, in a single volume of this size, is naturally not exhaustive (in the account of Millikan’s oil-drop experiments, for instance, the question of the validity of Stokes’ law is dismissed in a brief footnote), but the text is supplemented by well-chosen references to original papers. The value of the work is enhanced, for many classes of readers, by the inclusion of
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a good selection of numerical tables, ranging from atomic structure factors to data on sensitivities of photographic emulsions to electrons of different speeds. The numerical data quoted are generally based on the most recent determinations of the relevant fundamental constants-though, as a minor criticism, it appears somewhat inconsistent to quote the round figure of 300 volts as the equivalent of 1 E.S.U. of potential difference, while stressing the distinction between absolute and international electrical units. Taken as a whole, the book may be recommended as an excellent introduction to -and, for non-specialists, an adequate summary of-the greater part of experimental electronics. There was a real need for a compilation of this character, and Dr. Klemperer’s book fills a very definite gap in the literature of his subject. H. R. ROBINSON. Actualitbs Scientifiques et Zndustrielles, 51 et 52. By M. G. URBAIN. Theories chimiques, publiees sous la direction de M. G. Urbain. I e t 11. La coordination des atomes dans la molecule; la symbolique chimique. 51 and 52 pp. Paris: Hermann e t Cie, 1933. Price : 12 francs each. I n this beautifully and clearly written monograph, Professor Urbain, using a historical background, attempts to bring the theories of inorganic and organic chemists about the structure of chemical compounds to a common basis. In general, he thinks that the theories of structure in inorganic chemistry have rested on a molecular pluralisle basis, beginning with the electrochemical theory of Berzelius, and, after that was abandoned following the discovery of substitution by Dumas, revived in a modified form many years later in the coordination theory of Werner. He thinks of the structures of organic chemists as referring everything to attractions between atoms without any thought of electrical forces, beginning with the substitutions of Dumas, through the types of Gerhardt-Laurent is not mentioned-and the atomic linkings of KekulB. Frankland and Couper are omitted but a complete picture is not to be expected in so brief a monograph. Professor Urbain sums u p his conclusions in three sentences, (p. 40, Part 11): (1) Neutral molecules may be formed with electrovalent unions. (2) Neutral molecules may be formed with non-electrovalent unions. (3) When a molecule contains both electrovalent and non-electrovalent unions, such a molecule should be considered as a complex molecule in which the constituent parts belong to the first two classes. Among the “electrovalent” unions Professor Urbain includes the union between hydrogen and carbon in methane and many other unions which American and English chemists consider as covalent. He thinks of the electron as transferred from the hydrogen t o the carbon and t h a t there is hidden dissimule ionization in such cases (Part I, p. 26; Part 11, pp. 19 and 21). I n this he follows, without knowing it, the interpretation of Kossel’s electronic theory, which has been made the basis of articles in the Chemisch Weekblad by van Arkel and de Boer, published in a German translation. Such a point of view confuses covalences with genuine ionic valences, though the latter may be found in compounds in “semi-ionic” unions and in complex molecules. Closely connected with this confusion is his failure t o see (Part I, p. 32 and elsewhere), that Meisenheimer has demonstrated that the fourth and fifth valences of quinquevalent nitrogen are different. The fourth is a covalence similar t o the three covalences of ammonia, while the fifth is a positive ionic valence. I n a similar manner (Part I, p. 49), while he sees clearly that if the chlorine of triethylsulfonium chloride is united by a covalence to the sulfur atom t h a t atom would have ten instead of eight electrons in its outer shell, he has not understood
