REVIEWS 479 



several sections. I. Inorganic Preparations. — This is a useful section ; 

 instructions for the preparation of nearly 200 substances are given, including 

 a few colloids. II. Qualitative Analysis (Inorganic). — The reactions of 

 the common radicles and of some of the " rare " elements are given. A 

 course of analysis follows ; more attention might have been paid here to 

 optimum concentrations for reactions, but otherwise the course is complete 

 enough for the average student. III. Quantitative Analysis (Inorganic). 

 — This is subdivided into Gravimetric Methods, Electrolytic Methods, 

 Volumetric Methods, and Gas Analysis. The list of estimations is very 

 comprehensive. The description of the preparation of Baryta solutions 

 requires a little more extension. Insistence is laid on standardising at the 

 same temperature all measuring instruments used in volumetric analysis. 

 This is unnecessary, as suitable and instructive corrections can be applied 

 when instruments are calibrated at different temperatures. IV. Organic 

 Preparations. — Instructions for nearly 300 preparations are given. The 

 value of this section is enhanced by the fact that the chief properties of 

 many of the substances to be prepared are described. V. Organic 

 Analysis (Qualitative and Quantitative). — Qualitative analysis is dealt 

 with in eight pages ; this part could be improved by some notes on the 

 separation of organic compounds from each other. The subdivision on 

 Quantitative Analysis describes the estimation of elements and of the more 

 important radicles. VI. Physical Chemistry. — An elementary course is 

 condensed into some eighty pages. The value of this section would be increased 

 by including some of the E.M.F. measurements which have important applica- 

 tions in Physical Chemistry. 



The whole volume should be of much use to many classes of students. 



L. F. G. 



The Electronic Conception of Valence and the Constitution of Benzene. 



By Harry Shipley Fry, Ph.D., Professor of Chemistry and Director 

 of the Chemical Laboratory, University of Cincinnati. [Pp. xviii + 

 297, with numerous diagrams.] (London : Longmans, Green & Co., 

 1 92 1. Price 1 6s. net.) 



This series of monographs has hitherto consisted of " summarised accounts 

 of progress made in recent years " in various branches of Inorganic and 

 Physical Chemistry. The above book scarcely comes within the original 

 scope of the series, as it is essentially an account of the author's own views on 

 the electronic conception of valency. Other work in this field is summarised 

 in a bibliographical review of about 12 pages. In spite of the interesting 

 theory presented by the author, it is to be regretted that a complete summary 

 of modern ideas does not find a place in the monograph. The outlook on 

 this account is very circumscribed ; there is practically no discussion of the 

 idea of polar and non-polar valency, and the theories of Lewis and Langmuir 

 and the magneton theory of valency are completely ignored. The essential 

 weakness of the presentation is that no differentiation is made between 

 the valency forces operating in carbon compounds and those occurring in 

 compounds ionised in solution and in the solid state. 



Basing his theory of valency on the earlier ideas of Sir J. J. Thompson, 

 he develops the conception of positive and negative valency, and this idea, 

 as put forward by the author, is very suggestive. Evidence is adduced to 

 show that the occurrence of negative hydrogen and positive chlorine is 

 possible in carbon compounds. 



The major portion of the book is devoted to the benzene nucleus. In 

 his theory of the benzene ring he makes use of the Collie benzene formula, 

 making the alternate C and H atoms + and — charged respectively. The 

 author thus ascribes an electro-positive or electro-negative character to each 



