NA TURE 



245 



THURSDAY, OCTOBER 31, 1912. 



THEORIES OF SOLUTIONS. 

 Theories of Solutions. By Svante Arrhenius. 

 Pp. XX + 247. (New Haven: Yale University 

 Press; London: Oxford University Press, 

 1912.) Price I2X. 6d. net. 



THE publication of Prof. Arrhenius's Silliman 

 lectures on "Theories of Solutions," 

 delivered at Yale in the spring of 191 1, will be 

 welcomed by all who are interested in the present 

 position of physical chemistry. The book is of 

 special value because the author has dealt very 

 lightly with those aspects of his theory of " electro- 

 lytic dissociation " which have been discussed over 

 and over again during the last twenty-five years 

 and have occupied so large a space in nearly 

 all recent text-books of physical chemistry. Thus, 

 although many of his illustrations are drawn from 

 electrolytic solutions, only three of the eleven 

 lectures deal specifically with such solutions, 

 namely, those on "The Theory of Electrolytic 

 Dissociation," "Conductivity of Strong Electro- 

 lytes," and "Abnormality of Strong Electrolytes." 



A special feature of the lectures is the historical 

 method of treatment, which is adopted, not only 

 in the first lecture, on "The History of the Theory 

 of Solutions," but throughout the whole course. 

 The author is, indeed, anxious to demonstrate that 

 the newer views of the nature of solutions were 

 a natural and logical development from those that 

 had been in vogue previously, and seeks to dis- 

 claim the idea that he and his co-workers in this 

 field originated a revolution which was in any 

 sense a complete break with the past 



The most fascinating lecture of the series is 

 that on "The Modern Molecular Theory." To the 

 average chemist it will be a complete revelation 

 to know how accurately the actual masses of the 

 molecules have been determined in recent years. 

 These masses are recorded most conveniently by 

 determining the magnitude of the constant N, 

 the number of molecules in a gram-molecule, which 

 is, naturally, the same for all molecules. Three 

 methods used by Perrin and based upon the 

 behaviour of minute suspended particles gave 

 for \ the values 68 x 10^, 65 x lo^'^ ^n^j -j x 10^-; 

 three methods based upon the study of radio- 

 active substances, including, for instance, the 

 actual counting of a-particles, have given the 

 figures 62x10°^, 71 x lo^- and 71x102-. Other 

 methods have given 71 x 10^2, 62 x io~ and 

 62 X io23. It is indeed remarkable that nine 

 series of determinations should agree thus to- 

 gether, the extreftie range being onl)' +6 per cent. 



Other topics dealt with are "Suspension," 

 NO. 2244, VOL. 90I 



"Adsorption," "\'elocity of Reaction," " Equi- 

 libria in Solutions," and " The Doctrine of Energy." 

 In the introduction, the author expresses the 

 view that modern physical chemistry is largely 

 synonymous with "theoretical chemistry," one of 

 its chief functions being to express in mathematical 

 form the experimental measurements of physicists 

 and chemists; that he himself has not lost his 

 skill in this art is shown by the introduction of 

 some new formulae in the present volume; that 

 even more far-reaching results may flow from this 

 method of working is clear from the use which 

 has been made by Perrin, Lindemann and others 

 of the formulae developed within the last five years 

 by Einstein. 



It is a matter for regret that a book of small 

 dimensions should have been issued at so pro- 

 hibitive a price as to confine it very largely to 

 reference libraries. The trustees of the " Silliman 

 Foundation " would fulfil the purposes of the trust 

 with much greater efficiency if they could arrange 

 to circulate the printed lectures on more reason- 

 able terms to a much larger circle of readers. 



T. M. L. 



INTRODUCTIONS TO BIOLOGICAL STUDY. 

 {1) A Guide for the Study of Animals. By 



Worrallo Whitney, Frederic C. Lucas, Harold 



B. Shinn, and Mabel E. Smallwood. Pp. 



ix f 197. (Boston, New York, Chicago: D. C. 



Heath and Co.) Price 2s. 



[2) College Zoology. By Prof. Robert W. 

 Hegner. Pp. xxv + 733. (New York: The 

 Macmillan Company ; London : Macmillan and 

 Co., Ltd., 1912.) Price iis. net. 



(3) Einfilhrung in die Biologie. By Prof. Karl 

 Kraepelin. Dritte, verbesserte Auflage. Pp. 

 viii + 356. (Leipzig and Berlin : B. G. Teubner, 

 1912.) Price 4.80 marks. 



(ij.^T^HE teaching of biology is much more 

 J. widely spread amongst American than 

 among British schools, and the need for systema- 

 tised courses of instruction in natural history is 

 there greater than with us. In this work compiled 

 by science teachers of Chicago high schools a 

 graduated course of zoological teaching is drawn 

 up, beginning with observations on house-flies and 

 ending with some very good suggestions on the 

 use of domestic breeds of animals as object lessons. 

 So far as this suggested course goes, the book 

 may be of considerable help to teachers in search 

 of a suitable curriculum. The greater part of the 

 work is, however, devoted to lists of questions 

 that any good teacher could draw up without 

 assistance. Some of the questions are badly 

 worded or unanswerable ; for example, "Compared 

 with a hvdra, how many cells has an earthworm ? " 



K 



