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be both interesting and stimulating, but it can scarcely be claimed that a student 

 would obtain from a perusal of the volume an all-round and up-to-date acquaint- 

 ance with thermochemistry. The book, being simply a record of the author's 

 original investigations and conclusions, contains almost no reference to the work 

 of others ; it is noticeable that, while there is an exhaustive subject index, there is 

 no name index. So far as can be seen from a cursory inspection, there is not even 

 a reference to Berthelot's method of determining heats of combustion, and it must 

 be admitted that such limitations of the scope of the book, however excellent from 

 the author's point of view, somewhat impair its usefulness as a general text-book. 



Again, owing partly to the fact that Prof. Thomsen's collected researches were 

 published by 1886, before the electrolytic dissociation theory was brought forward, 

 partly, perhaps, to the author's own views on the subject, the application of that 

 theory in interpreting the thermochemical behaviour of electrolytes is not 

 recognised in this volume. The translator, whose work is generally satisfactory, 

 tries to make amends by one or two verbal alterations, but this of course is only a 

 partial remedy, and the reader is asked in the translator's preface " to place the 

 modern interpretation on the figures given should he so desire." Surely this 

 leaves the student rather in the lurch ! 



The bearing of the electrolytic dissociation theory on the thermochemical 

 behaviour of electrolytes is very direct, and receives perhaps its most important 

 illustration in the fact, elucidated from Thomsen's figures and recently emphasised, 

 that the heats of formation of the salts in dilute solution are additive quantities. 

 This is a notable result, especially when it is borne in mind that no such relation- 

 ship exists in reference to the heats of formation of the solid salts or their heats 

 of solution. For a discussion, however, of these and allied thermochemical results 

 in the light of modern theories, one searches Prof. Thomsen's book in vain. 



The expectations that were once entertained as to the importance of thermo- 

 chemical investigations have not been realised. Specially is this the case in 

 reference to the principle of maximum work — generally associated with the name 

 of Berthelot, although Thomsen himself in the volume under review claims to 

 have propounded it thirteen years before Berthelot. In any case, the principle of 

 maximum work has lost its significance, and it is now recognised that the quantity 

 of heat evolved in a chemical reaction is not an accurate measure of the affinities 

 of the reacting substances. The value of thermochemical data in deciding 

 questions of constitution has likewise been exaggerated, and to-day there are 

 other physico-chemical methods which are much more serviceable in this respect. 



But even when due allowance is made for the fact that thermochemical 

 research has not yielded results of such significance as was at one time anticipated, 

 there is no doubt that the study of the heat effects which accompany chemical 

 changes will always be an important branch of investigation. At the present 

 juncture, when Berthelot is dead, and Thomsen has retired from active work, one 

 wonders who the thermochemists of the immediate future are to be whose work 

 will rank with that of these two masters. 



J. C. Philip. 



Thermodynamics of Technical Gas Reactions. By Fritz Haber. Translated 

 by Arthur B. Lamb. [Pp. xix + 356.] (London : Longmans, Green & Co., 

 1908 ; price io.y. 6d.). 



Physical Chemistry, on its theoretical side, is largely based on thermodynamics, 

 and the present volume furnishes a fresh example of this close relationship. More 

 than that, it represents an endeavour to bring thermodynamics into touch with 



