REVIEWS 169 



conifers or the citrus species are distilled, the distillates are found to contain a 

 mixture of substances, which are classed under the general head of ethereal oils." 

 This statement really implies that "Stockholm tar" and acetic acid are ethereal 

 oils, which is probably not quite what the author intended. Again, on p. 159, there 

 is this statement : " The monocotyledon species of plants seems to be the richest 

 in members whose tissues produce these substances (alkaloids)." This, to say 

 the least, is a very unhappy use of the word "species." These points and others 

 like them should be put right in issuing a revised edition. The book can be 

 recommended to students and to teachers as giving a good summary of recent 

 work in the subjects with which it deals. 



T. A. H. 



Outlines of Physical Chemistry. By George Senter, Ph.D., B.Sc. [Pp. 

 xvii + 369.] (London : Methuen & Co. 3s. bd.) 



This volume is a welcome addition to the available text-books of physical 

 chemistry. Although it professes to be of an introductory character and the 

 knowledge of mathematics required by the reader is of an elementary descrip- 

 tion, the author has contrived, within these limits, not only to give an excellent 

 outline of the subject, but also to fill in much interesting detail. His familiarity 

 with the student's point of view enables him to expound with commendable 

 clearness the leading principles of this attractive branch of science. 



The employment of physical methods in solving chemical problems crops 

 up primarily in the determination of atomic weights, and the author has done 

 well to deal with this fundamental problem in the first chapter. It is a problem 

 which the average student usually fails to grasp, and it is essential that his 

 attention should be turned once more in this direction before he proceeds to 

 consider matters belonging more especially to the province of physical chemistry. 



Dr. Senter has followed up his introductory chapter with others on the 

 properties of gases, liquids, and solutions. This arrangement is much preferable 

 to the one favoured in some quarters, by which the reader is first introduced 

 to the conceptions of velocity and equilibrium. There is no doubt something 

 to be said for the latter method of beginning the study of physical chemistry, 

 but it is infinitely more difficult for the elementary student. 



The author's arrangement of the material in the later portions of his book 

 is open to some criticism. It is difficult to see why a chapter on "Thermo- 

 chemistry" should be placed between one on "Dilute Solutions" and another 

 on " Equilibrium in Homogeneous Systems." Again, the discussion of electrolytic 

 solutions, instead of following immediately the chapter on dilute solutions, is 

 postponed until "Thermochemistry," "Equilibrium in Homogeneous Systems," 

 '• Heterogeneous Equilibrium " and " Velocity of Reaction " have been expounded. 

 Surely, on historical as well as logical grounds, the electrolytic behaviour of 

 acids, bases, and salts ought to be discussed in close conjunction with their 

 abnormal osmotic behaviour. 



The general excellence of the book, however, is scarcely touched by these 

 criticisms, for in regard to the best way of expounding any given scientific 

 facts there are bound to be different opinions. 



One very gratifying feature of Dr. Senter's volume may finally be mentioned, 

 and that is the addition of a section on " Practical Illustrations " at the end 

 of each chapter. This should certainly be of great service to the student, 

 perhaps also to the lecturer on physical chemistry. 



J. C. Philip. 



