292 



NA TURE 



[July 26, 1900 



Chapter iv. we have a systematic account of the action 

 of fluorine on . the non-metallic elements and on some 

 of their compounds, together with a somewhat de- 

 tailed study of the non-metallic fluorides. The action 

 of fluorine on the metals and their compounds forms 

 the subject-matter of Chapter v., the organic fluorine 

 compounds receiving treatment in Chapter vi. The 

 last chapter in the book deals with the atomic 

 weight of fluorine, the volumetric composition of hydro- 

 fluoric acid, the action of fluorine and hydrofluoric acid 

 on glass, and the position of fluorine in the system of the 

 elements. The author definitely places fluorine at the 

 head of the halogen family, sufficient stress, however, 

 being laid on the points in which fluorine resembles the 

 elements of the oxygen family ; such as the ease with 

 which it unites with carbon, and the analogies exhibited 

 by hydrofluoric acid to some dibasic acids. A short sum- 

 mary of the properties of fluorine concludes the volume, 

 and for frontispiece there is an excellent portrait of the 

 author. 



The book is as interesting as a monograph can well 

 be, and M. Moissan has earned the gratitude of all 

 chemists by thus placing before them a connected record 

 of one branch of his splendid activity. J. W. 



OUR BOOK SHELF. 



A Text-Book of Physical Chemistry. By Dr. R. A. 



Lehfeldt. Pp. xii-t-308. (London: Edward Arnold, 

 1899-) 

 A FEW years ago the teacher of physical chemistry seek- 

 ing a suitable elementary text-book, dealing with the 

 more recent developments of the subject, which he could 

 put into the hands of a class of students approaching the 

 study of physical chemistry for the first time, was some- 

 what embarrassed to find one. This state of things is 

 now changed for the better by the recent appearance of 

 several very excellent works ; among these Dr. Lehfeldt's 

 book will take a high place. The author explains in his 

 preface that the book " is intended to contain what a 

 student — with limited time and many subjects to learn — 

 may usefully read. It is by no means written to suit any 

 examination, but still is written with the practical require- 

 ments of students in view." 



Dr. Lehfeldt has succeeded in avoiding the unessential 

 and in explaining the fundamental ideas of modern 

 physical chemistry in a thoroughly lucid manner, so that 

 a student who has grasped the contents of this book will 

 experience little difficulty in appreciating the meaning of 

 the larger handbooks or original memoirs. 



An introductory chapter on physical units will be useful 

 to chemical students, who are, perhaps, apt to be slipshod 

 in such matters. This is followed by a chapter on mole- 

 cular weights in gases and solutions, which includes 

 electrolytes and the ionic theory, and by a very well- 

 considered chapter on the connection between physical 

 properties and chemical constitution. The principles of 

 thermodynamics are then explained ; and the two laws 

 {a) of chemical equilibrium in a system of perfect gases 

 at constant temperature, and {b) of the influence of tem- 

 perature on chemical equilibrium are deduced from them. 

 This chapter presupposes some knowledge of the ele- 

 ments of the calculus, but any student who wishes to 

 understand physical chemistry must make up his mind to 

 acquire the small amount of mathematical knowledge 

 requisite. 



The applications of the two thermodynamic theorems 



NO. 1604, VOL. 62] 



to chemical change and equilibrium in homogeneous and 

 heterogeneous systems are then taken up. This treat- 

 ment has the great advantage that the whole of the 

 phenomena can be grouped in a very simple way, the . 

 close relationship of chemical and physical change is 

 clearly brought out, and the student is not bewildered by 

 the apparent multiplicity of the phenomena. The book 

 concludes with a brief but most interesting chapter on 

 the theory of the galvanic cell, and the connection be- 

 tween electromotive force and chemical affinity. The 

 book may be unhesitatingly recommended as one of the 

 best of its kind. 



The only misprint we have noticed occurs on p. 141, 

 line 18, where "increases'' is written in place of 

 "decreases." T. E. 



An Introduction to Analytical Chemistry. By G. G. 

 Henderson, D.Sc, M.A., and M. A. Parker, B.Sc. 

 Pp. 228. (London : Blackie and Son, Ltd., 1899.) 



This is a compact work covering the ground of 

 ordinary qualitative analysis as well as the tests for a 

 number of organic substances, and also containing an 

 account of the most important processes of quantitative 

 analysis. 



Without being designed on any new plan or being 

 explanatory to the fullest extent, the book is written in 

 a scientific spirit. The authors state that they have 

 made free use of the works of Dittmar and others, and 

 it is perhaps not uncomplimentary to remark that the 

 influence of that sterling chemist is apparent in the 

 book. 



The directions for work are clear and practical, and 

 the analytical methods quite satisfactory. Perhaps the 

 least useful part of the book is that dealing with organic 

 substances and their separation from mixtures. This 

 branch of analytical art is very difficult, and the par- 

 ticular form of it, which has been encouraged by certain 

 examining bodies, has brought disaster to many a good 

 student. It is difficult to understand what useful pur- 

 pose is served by the efforts of second-year students to 

 prepare for recognising the constituents of, say, a mixture 

 of urea and an inorganic salt. It is of no importance 

 to medical men, it does not help the teaching of organic 

 chemistry, and it crowds out practical work which would 

 be of real value. The examination of such mixtures is 

 a matter for an analyst of mature knowledge and ex- 

 perience. , A. S. 



Maryland Weather Service. Vol. i. Pp. 566. (Balti 

 more : The Johns Hopkins Press, 1899.) 



The Maryland State Weather Service was established in 

 1892, and its reports and climatic charts are favourably 

 known to meteorologists. In 1896 a plan of closer co- 

 operation between the National and State Weather 

 Bureaux was proposed by Prof. W. L. Moore and adopted. 

 This marked the commencement of a new and very im- 

 portant period in the history of the Service, and the 

 present volume is the first published since the two 

 organisations have been in close connection. The 

 energies of the Service are now to be devoted chiefly to 

 the publication of special reports on the climatology of 

 the State, and if the volume before us is to be taken as 

 an earnest of future ones, we may be pardoned a feeling 

 of envy at the sumptuous way in which scientific work of 

 this kind is presented to the public in America. We 

 notice that it is proposed to publish in the near future a 

 full account of the climatic features of Maryland, in which 

 the physiography, meteorology, hydrography, medical 

 climatology, agricultural soils, forestry, crop conditions 

 and the fauna and flora of the State will be considered. 



The present volume is confined to the physiography 

 and meteorology, and includes an introduction by Prof. 



