May 3, 1906] 



NA TURE 



but as they dilTor in many respcrts from the En^flish, 

 the chief interest of the book for Enf,'Iish readers of 

 French aj^ricultural literature will lie in its admirable 

 exposition of the scientific principles underlying prac- 

 tice. The book is well illustrated on the whole, but 

 in some cases the photographic reproductions can 

 hardly be regarded as truly illustrative. Otherwise 

 wc have nothing but admiration for the manner in 

 which Prof. Diffloth in this first volume has given 

 effect to the aim of the new French agricultural 

 encyclopaedia. 



INORGANIC CHEMISTRY FOR STUDENTS. 



Outlines of Inorganic Chemistry. By Frank Austin 

 Gooch and Claude Frederic Walker. Pp. xxiv+514. 

 (New York : The Macmillan Co. ; London : Mac- 

 millan and Co., Ltd., 1905.) Price 75. 6d. net. 



THE authors say in the preface that their aim is 

 " to introduce the student to chemistry by con- 

 sideration of the simplest and fewest things." Their 

 intention is laudable enough, but it may be questioned 

 whether their plan of entering into a long discussion 

 of " the consecutive development of the principles upon 

 which systematic chemistry rests," before taking 

 up the descriptive part of the subject, is one which 

 can be commended. 



The first 233 pages of the book are entirely devoted 

 to theoretical matters, and a wide range of subjects 

 is included. Beginning with an exposition of the 

 outward characteristics and quantitative laws of 

 chemical combination, the authors pass on to discuss 

 balanced actions, chemical equilibrium, and the phase 

 rule. Then follows a short chapter on specific heats 

 and thermochemistry, after which the student is " in- 

 troduced " to atoms, molecules, ions, and electrons. 

 Finally an attempt is made to teach him something 

 about the kinetic theory of gases, the properties of 

 solutions, the theory of valency, constitutional 

 formute, physical isomerism, and stereochemical rela- 

 tionships. Whatever fault the reader may have to 

 find with the mode of presentment in this part of the 

 book, he will have no reason to complain of lack of 

 variety. The authors have attempted too much, and 

 have sacrificed clearness to the exigencies of space. 

 The beginner will, we fear, be confused, and the more 

 advanced student will find the treatment of the subject 

 Inadequate and superficial. 



Without attempting any detailed criticism of these 

 theoretical chapters, which would indeed serve no 

 useful purpose, we may give one or two examples of 

 what we think an unsatisfactory way of presenting 

 ideas to the beginner. In speaking of chemical 

 changes, the authors make use of the term " factor " 

 to denote "substances which enter into reactions"; 

 thus we read of " the change of the factor mercuric 

 oxide into the elementary products mercury and 

 oxygen by heat," and so on. Nor do we think their 

 invention of the clumsy expression " mass-unit 

 iL'eii;lit " of an element will at all help the student to 

 grasp the idea of " atomic weight." The beginner 

 w'ill probably be at a loss to understand why the com- 

 NO. 1905, vol.. 74] 



pound NO is called " nitrogen dioxide," whilst CO* 

 is called " carbon monoxide." 



The descriptive part of the book (493 pages), which- 

 is arranged in accordance with the periodic system, 

 calls for little comment. Much valuable space is- 

 wasted on elaborate constitutional formulae, the- 

 majority of which are advanced without the slightest: 

 attempt at proof or criticism. When, however, the 

 authors do discuss such matters they are not always 

 convincing, as the following example will show : — 



" The possible constitution of phosphorus pentoxide- 

 may be made a matter of discussion. If we assign, 

 to phosphorus the symbol 



P = P 



II II 

 = P> 



suggested by the specific gravity of phosphorus in 

 vapour condition, we might conceive phosphorus pent- 

 oxide, formed by the complete oxidation of phos- 

 phorus, to have a similar constitution. 



0000 



Pf-O/P 



Of the molecular weight of phosphorus in solid con- 

 dition, or of phosphorus pentoxide, we have no know- 

 ledge, so we find it convenient to represent both sub- 

 stances by the simplest possible equivalent symbols, 

 P and P,'0,,." 



We thought that the once prevalent idea of the 

 preferential combustion of hydrogen in hydrocarbon 

 flames had long since been discarded ; the authors 

 however, still believe in it, for in discussing the 

 luminosity of the acetylene flame they tell us that the 

 gas " burns from an ordinary gas jet with a flame 

 which is luminous, but very sooty from finely divided 

 free carbon, the hydrogen burning first 

 2C,H3 + 0, = 2C, + 2H,0." 



In short, we find much in this book which would' 

 deter us from recommending it as a clear and trust-- 

 worthv exposition of chemical facts and theories. 



W. A. B. 



OUR BOOK SHELF. 

 Collodion Emulsion. By Henry Oscar Klein. Pp.. 



95. (London : Penrose and Co., 1905.) Price 5s. 



net. 

 The advent of gelatin plates has almost driven 

 collodion out of the photographic world. The wet 

 collodion process has all along retained its position in 

 some kinds of photo-mechanical work, but collodion 

 emulsions seemed to have no place left for them until 

 a few years ago their advantages for certain technical 

 purposes were insisted on, and the publishers and 

 author of this volume did a good deal towards re- 

 introducing them into this country on a commercial 

 basis. .\s" collodion emulsion can now be purchased 

 the author has very little to say about the preparation 

 of it ; he only quotes two or three formulae from other 

 workers. The volume must be regarded as a guide 

 to the practical user of commercial emulsions. Their 

 applications in the making of ferrotypes, lantern 

 slides, opals, and transparencies, and for photograph- 



